Neuroimaging During Pregnancy

During pre, there are some alterations in physiological state of pregnancy which leads to variety of neurological problems.
Pregnant patient with neurologic problems carries both diagnostic and therapeutic challenges.
The physicians often require some form of neuro imaging as part of their ongoing evaluation.

Safety of CT and MRI during pregnancy.
Whenever the imaging study in a pregnant patient is considered, risks to the fetus must be balanced with the health of mother.

CT ?
Off course carries risk of radiation to fetus.
The harmful effects of radiation depend on the stage of gestation, the total dose of radiation, and the rate.
As per animal studies, highest sensitivity appears to be during the period prior to conception when developing embryo has not yet been implanted in the uterus, during these first 2 week there is all-or-nothing effect that is either no effect or demise of the embryo.
During organogenesis, 3rd to 8th wk after conception, risks to the developing embryo is variable ranges from congenital malformations to growth retardation or neonatal death.
During the fetal period of development, 6 weeks after conception to birth, irradiation is unlikely to result in gross malformations. However, may result in mental retardation.
As per available data, the dose required to have mental retardation is 12–20 rad which is far higher than the dose achieved in today’s diagnostic procedures.
The fetal radiation dose during CT Brain of mother is less than 0.01 rad, whereas CT abdomen is 0.25–2.5 rad which is far low.
Some believe than there is increase risk of childhood cancer like leukemia but the figures from recent studies mention that there is extremely small added risk for children of patients who have undergone diagnostic imaging during pregnancy. Even multiple CT of the abdomen would only minimally increase the natural risk of childhood cancer.

Now what if patient is found pregnant after CT study is done? 
1. She should she be informed of the fetal radiation.
2. She and her family needs to counseled that exposure to less than 5 rad …is not associated with definite risk of spontaneous abortion, cong malformations, or mental retardation. This over concern should not prevent medically necessary procedures from being performed.

MRI ?
As far as neuroimaging i e Brain and Spine in concerned MRI often preferable to CT and is considered to be safe during pregnancy.
But one should delay elective MRI if possible as its believed that there is a strong magnetic field, minimal increase in body temperature, and there is lot of noise that may affect developing chochlea of fetus.
Intra venous Contrast ?
The problem is that we don’t have well-controlled studies in pregnant women, but animal studies have failed to show association of teratogenicity or mutagenicity with use of contrast.
However CT contrast is rated as a class B drug where as MRI contrast is rated as a class C drug by the FDA so  better avoid both unless no alternative exists.
Contrast during Lactation ?
Let it be CT or MRI, estimated delivery of contrast from mother to baby via breast milk is extremely low so there is no need to stop breast feeding following CT or MRI Contrast.


Neurologic Diseases Associated With Pregnancy

Pregnancy causes changes in the hemodynamic, endocrine, and hematologic systems, which may predispose to stroke during pregnancy.
Neuroimaging features of stroke are not going to change in pregnant and non pregnant pt.

Cerebral Venous Thrombosis
Presentation is often headache, seizures, encephalopathy, papilledema, or focal neurologic deficits.
MRI is investigation of choice as there is no radiation, its high Resolution and have MR Venography option which is possible without contrast. No need of keeping patient Nil by mouth (NBM).
MRI can elegantly demonstrate thrombosed dural venous sinus or deep cerebral vein. Associated infarction and intraparenchymal hemorrhage.

Thrombosed superior sagittal sinus, note low signal intensity thrombus on GRE.  

Thrombosed right parietal para sagittal cortical veins with low signal intensity thrombus on GRE

 A case of deep cerebral venous thrombosis_ bilateral thalamic venous infarcts. Thrombosed straight sinus not visualised on MR Venogram. 

Preeclampsia and Eclampsia
A multisystem disorder seen in the later stages of pregnancy / in the first 6 to 8 weeks after delivery.
Exact etiology is not clear, but the circulating toxins released from the placenta believed to cause vascular pathology.
Preeclampsia, a less-severe form of the disorder, occurs in ~5% of pregnancies, characterized by hypertension and proteinuria. Clinically usually asymptomatic, may present with headaches, sudden or unusual severe edema, visual changes.
Eclapsia , a severe form characterized by seizures.
MRI findings of preeclampsia and eclampsia are same, the combined term used in imaging diagnosis is Hyper tensive encephalopathy /  Posterior reversible encephalopathy.

MRI Brain axial FLAIR images show bilateral fronto parietal T2 white matter hyper intensities without restricted diffusion, and with normal MR Venogram of Brain which is very typical of  Posterior Reversible Encephalopathy

HELLP, a severe form seen in ~ 10% of patients and is a life-threatening condition characterized by hemolytic anemia, elevated liver enzymes, and low platelet count.
This low platelet count can lead to intra parenchymal bleed without any CVT on MR Venogram.

A typical case of HELLP, low platelet count and raised liver enzymes. 
MRI Brain shows left frontal bleed with left fronto parietal sub dural hematoma. Normal MR Angiography and Venography of Brain, done to rule out any associated vascular malformation.

Postpartum Angiopathy
A reversible cerebral vasoconstriction syndrome involves medium-sized intracranial arteries.
Patient often present with thunderclap headache, acute as well as focal neurologic deficits.
MRI Brain with MR Angio investigation of choice.  No contrast. No NBM.
MRI may demonstrate recent infarcts along border zones. Stenosis / vessel occlusion on MR Angio.

MRI Brain diffusion shows multiple recent infarcts along bilateral cortical border zones. MR Angiography of Brain shows multifocal intracranial stenosis. 

Meningioma
Meningiomas may dramatically increase in size during pregnancy as some of them represent hormonal receptors.
Presentation depends on its size and location, varies from elevated intracranial pressure, visual impairment with optic nerve atrophy to seizure.

A known case of Sphenoid wing meningoma.

Now admitted with recent onset seizures while pregnant, the on admission repeat MRI Brain shows same left side Sphenoid wing meningioma, but this time it was marginally increased in size with marked perilesional odema which was absent in previous MRI. 

Choriocarcinoma with Metastasis 
A malignant trophoblastic tumor.
May occur after a normal pregnancy, or can be seen in the context of abortion, molar or ectopic pregnancy.
Can metastasize to the liver, lung, or in 10% of cases to the brain.
Choriocarcinoma and its mets a highly vascular tumor and therefore very susceptible to bleed.
Presentation may be headache, focal neurologic deficits, seizures, encephalopathy, raised ICT.

A case of Choriocarcinoma with hemorrhagic metastasis in Brain

Pituitary Apoplexy
During pregnancy the pituitary gland tends to grow in size and some time it outstrips its vascular supply leading to hemorrhagic and/or ischemic changes.
Presentation is usually sudden headache, nausea, or vomiting, loss of consciousness.
Due to the close proximity of the pituitary gland to the optic chiasm and cranial nerves III, IV, and VI may present with  multiple CN Palsy.

A case of pituitary apoplexy showing enlargement of pituitary with bleed on MRI mid sagittal non contrast T1w section. 

Sheehan syndrome
A hypopituitarism secondary to severe blood loss and hypo volemic shock during labour resulting in Ischemia and necrosis of pituitary .
On MRI, lack of normal enhancement on post contrast images is a diagnostic clue.
Once bleed or ischemia resolves, on follow-up imaging one may find Empty sella due to loss of tissue volume.

MRI Brain, mid sag T2w sections shows Roomy hypophyseal fossa occupied by Csf. 

Pituitary flat at the floor near posterior wall of sella with an abnormal height less than 2mm.

Lymphocytic Hypophysitis
An autoimmune condition of the pituitary occurs in late pregnancy or the postpartum period due to Lymphocytic infiltration of the pituitary gland, infundibulum.
Enlargement of pituitary gland with abnormal enhancement on MRI is a diagnostic clue.

Wernicke's Encephalopathy
Caused by thiamine deficiency.
Common in chronic alcoholics however pregnant patients with hyperemesis gravidarum due to malnutrition due to nausea and vomiting and increased fetal metabolic demand for thiamine, land up with thiamine deficiency.

A case of Wernike's Encephalopathy, MRI Brain Axial FLAIR images at the level of brain stem shows typical peri aqueductal involvement of mid brain and hypothalamic T2 hyper intensities. 

Characterized by triad of Acute encephalopathy, Ataxia, and Ophthalmoplegia or Coma alone.
With early diagnosis, can be rapidly reversed with IV high dose of thiamine and fatal if left untreated.
MRI is investigation of choice.

Multiple Sclerosis
Commonly affects 20 to 50 Years females i e reproductive  age group.
Nothing specifically different in the neuroimaging of pregnant / non preg MS patients however pregnancy, affect the relapse rate, as relapses decrease in frequency throughout pregnancy  but increase in the postpartum period.
Increased estriols level during pregnancy result in  T2 mediated immune shift in MS.
MRI investigation of choice.

Case of MS, MRI Brain Axial and Sagittal T2w images of Brain showing plaques of demyelination in bilateral fronto parietal peri ventricular white matter, involving corpus callosum. Sagittal T2 w images of spine of same patient shows faint T2 hyper intensities of demyelination involving cervico dorsal cord.

Pregnancy-related Back Pain
Backache is common during pregnancy cause can be  hormone-induced laxity of spinal ligaments, Gravid uterus exerting pressure on the lumbosacral plexus or increased lordosis in pregnancy.
MRI is the best, can visualize spine , spinal cord as well as nerve roots which is not possible with CT.
Better post pone MRI too.
But Strong indications for MRI are cauda equina syndrome, acute weakness, radiating pain, bowel bladder involvement.
MRI may reveal Disc herniation causing cord, cauda equina or nerve root compression and cord demyelination in patient of lower limb weakness.

MRI Lumbar spine sagittal and axial T2 w images at L5-S1 show a left para central disc extrusion causing obvious compression of left traversing S1 nerve root in lateral recess. 

MRI Dorsal spine sagittal and axial T2w images shows a focal disc protrusion causing cord compression.

MRI Cervico dorsal spine, sagittal T2w images show abnormal multi segmental contiguous intramedullary T2 hyper intensity suggestive of cord demyelination. 

Epidural hematoma can occur rarely in association with pregnancy, either spontaneous related to increased abdominal pressure during delivery or as a complication of epidural anesthesia.

MRI Lumbar spine, Sag T1 and T2w images : Case of posterior spinal epidural hematoma causing significant canal stenosis at L2-3 disc level with marked compression over thecal sac and nerve roots of cauda equina. 

Conclusion
As far as safely is concerned MRI is safe than CT. However post pone both CT as well as MRI if possible.
As far as Neuro imaging is concerned the treating physician, radiologist should be aware of these conditions which are common during pregnancy. Even the MRI technician should be trained for this to do necessary changes in a given study depending upon the findings while doing MRI like running Angio or Veno sequence as and when required.

Post Laminectomy site Adhesion / Herniation of Cord MRI

A post operative case came for follow up imaging. Clinical details not available.

This MRI Dorsal spine shows:
E/o laminectomy, faint intra medullary T2 hyper intensity of focal cord Gliosis.
Focal posterior displacement of cord at laminectomy site.
MRI repeated in prone position, cord is persistently seen displaced posteriorly at laminectomy site _ possible with adhesion or herniation.

Anterior Thoracic Spinal Cord Adhesion and Herniation on MRI

A 30 y male presented with intermittent backache, mild progressive paraplegia. Anterior spinal cord dysfunction on neurological examination. No obvious dorsal column involvement. 

MRI spine shows anterior thoracic cord displacement with flattening. Wide sub arachnoid space dorsal to cord iso intense to Csf.

Imaging wise possible DD:
1. Posterior Arachnoid cyst.

2. Idiopathic Anterior Spinal Cord Herniation / Adhesion.

ANTERIOR SPINAL CORD HERNIATION / ADHESION

In a study of middle aged patients of both sexes presenting with chronic progressive anterior cord dysfunction with imaging demonstration of anterior thoracic cord displacement is either by a posterior arachnoid cyst or anterior dural adhesion / herniation. Cord thinning was frequently found without signal abnormality in cord.

A dorsal arachnoid cyst is one of the most important entities included in the differential diagnosis of idiopathic spinal cord herniation. If findings on standard MR images are equivocal, phase-contrast MR imaging or CT myelography may be helpful for detecting the free flow of CSF and excluding an arachnoid cyst.
If it’s an obvious posterior Arachnoid cyst, needs decompression for sure. Cases without appreciable Arachnoid cyst can be associated with either anterior spinal cord herniation or adhesion. 

Mechanisms leading to anterior spinal cord herniation described in literatures are congenital anterior dural defects, duplication and rarely trauma. A dural defect cannot be demonstrated on MRI, although absent visualization did not exclude a defect at surgery.

A typical case of anterior spinal cord herniation from AJNR

In patients in whom no defect is found at surgery; instead, the cord can be anteriorly tethered by arachnoid or dentate adhesions. The thoracic anterior spinal cord adhesion syndrome (TASCAS) is a novel term to describe patients presenting in this way. 

The frequency with which adjacent disc abnormality is seen in surgical case report supports the role of disc disease in the aetiology of TASCAS. One possible mechanism would involve inflammatory change, incited by a diseased disc, causing adhesions with the adjacent dura. The anterior cord surface becomes tethered by associated arachnoid and/or dentate ligament adhesions. Subsequent disc resorption could result in formation of a dural retraction pocket predisposing to progressive pathological cord displacement and subsequent herniation. Other factors may also be contributory, such as the relatively anterior position of the cord in the mid-thoracic spine due to the normal physiological thoracic kyphotic status, bringing the spinal cord into close apposition with the discovertebral complexes.

MRI is considered sufficient for the diagnosis of Posterior Arachnoid cyst Vs Anterior Cord herniation / Adhesion in most cases. Use of three-dimensional volume T2* sequences (such as CISS /FIESTA) as in this case provide high-resolution images which aid the decision making while limiting the need for invasive procedures.
Even with these high-resolution series, the exact nature of the abnormality can only really be defined at surgery. In any case, the decision whether to operate or not is ultimately made on clinical rather than radiological grounds. 

If a surgical approach is to be contemplated, the anterior aspect of the cord should be visualized intra operatively, regardless of the degree of radiological certainty in the pre-operative differentiation between hernia or adhesion.

Appropriate initial imaging studies in Neuro as per clinical problems

                      Clinical problem                                             Modality

Fractures / Bony lesions of Skull	CT brain with bone window
Major head trauma	CT (neurologically unstable); MRI (neurologically stable)
Mild head trauma	Observe; CT (if persistent headache)
Acute hemorrhage (Bleed)	Non contrast CT
Suspected intracerebral aneurysm or AV Malformations	MRI Brain with (3D TOF Non Contrast) MR Angiography
Hydrocephalus	Non contrast CT < MRI
Transient Ischemic Attack	Non contrast CT, MRI if vertebro basilar findings; consider carotid Doppler if bruit present.
Recent giddiness and walking imbalance	MRI Brain with 3D TOF Non Contrast MR Angiography
Acute stroke (suspected hemorrhagic)	Noncontrast CT
Acute stroke (suspected non hemorrhagic)	MRI Brain with (3D TOF Non Contrast) MR Angiography
Multiple sclerosis	MRI Brain and Whole Spine screening for Cord
Tumor or metastases	MRI with Contrast
Aneurysm (chronic history)	3D TOF Non Contrast MR Angiography or Contrast CT Angiography
Abscess	Contrast CT / MRI
Preoperative for cranial surgery	Contrast angiography
Meningitis	Lumbar tap; CT Brain only to exclude complications
Seizure (new onset or poor therapeutic response)	MRI (Epilepsy protocol)
Seizure (febrile or alcohol withdrawal without neurologic deficit)	CT / MRI sos
Neurologic deficit with known primary tumor elsewhere	MRI if associated sensorineural findings
Vertigo (if suspect acoustic neuroma or posterior fossa tumor)	MRI with thin sections for Cranial Nerve imaging
Headache	CT Brain covering Para nasal sinuses
Dementia	Nothing, or MRI Brain
Alzheimer’s disease	Nuclear medicine SPECT scan
Sinusitis	CT / MRI Brain with limited axial sections to cover sinuses

Reference: Mettler, Essentials of Radiology, 2nd ed.

DDs of Owl's Eye _ Spinal cord T2 hyper intensities on MRI

There is not much mentioned about this sign but whatever is available in literatures and case reports where they have described this finding and in view of clinical scenario they have tried to attribute this finding to one particular condition or cause. Most of them have associated this finding with spinal cord infarction, however this finding is not specific or pathognomonic for spinal cord infarction.

I have tried to elaborate list of other remote conditions and causes which can present with such finding on MRI or follow up MRI irrespective of clinical settings. Most of them are with reference and few of them are through my personal experience.

What is Owl's Eye Sign? 
An abnormal intra medullary T2 hyper intensity in the region of anterior horn cells of spinal cord, as two white dots, one in each half of cord on axial T2w MRI images in the background of normal gray coloured spinal cord.

This is totally different from ‘Winking  Owl’  sign
Winking owl sign  is related to vertebral metastases, a reliable sign of osteolytic spinal metastases on AP radiographs corresponds to loss of the normal pedicle contour. The appearance of unilateral pedicle absence has been likened to that of a winking owl with the missing pedicle being the closed eye, the contralateral pedicle being the open eye and the spinous process being the beak.

DDs of Owl's Eye in spinal cord. 

1. Spinal cord Infarction 
The vascular supply to the spinal cord is primarily composed of one anterior and two posterior spinal arteries, which extend along the length of the spinal cord in a variable manner. The anterior and posterior spinal arteries are connected by a pial plexus that extends around the circumference of the spinal cord. At many levels, the anterior and posterior spinal arteries receive vascular contributions from the radicular arteries, which course along the nerve roots and enter the spinal canal. Thirty-one pairs of radicular arteries exist. The anterior spinal artery gives rise to central arteries at multiple levels; these arteries supply the anterior horn cells and the anterior aspect of the lateral columns on both sides of the spinal cord.
Two major forms of spinal cord infarcts are recognized. The first involves the interruption of supply by the radicular arteries or artery of Adamkiewicz and is characterized by unilateral or bilateral infarcts of the anterior or posterior spinal arteries. The second one is caused by diffuse hypoperfusion and is manifested by central or transverse infarcts.
Recognized causes include spinal and aortic surgery, hypotension, vertebral artery dissection, embolism, vasculitis, and cocaine abuse. In about half of cases, infarction occurs immediately after a movement, such as back extension, an arm movement or a Valsalva maneuver, possibly causing mechanical stress on a radicular artery.

2. Fibrocartilaginous emboli
Rapid onset of spinal cord symptoms from retrograde flow of emboli from a herniated nucleus pulposus into the anterior spinal artery or spinal veins during straining, causing an anterior spinal artery syndrome (Wilmshurst et al 1999). There is back or neck pain but often no history of trauma, followed by sudden (minutes to hours) onset of weakness and incontinence. This is more common in women than men and is associated with anterior cord lesions on MRI and anterior horn cell fallout on electrophysiologic testing. Cord swelling on MRI is associated with a collapsed disc at the level of the cord deficit, usually in the cervical region (Tosi et al 1996). The CSF is normal. There is no associated viral syndrome. Recovery is unlikely.

3. Resolved Cord Contusion
A resolved spinal cord contusion on follow up imaging can have similar appearance due to Gliosis. History of trauma particularly hyper flexion injury needs to ruled out clinically. Vertebral collapses may be an associated finding on MRI.

4. Poliomyelitis and Motor Neuron Diseases 
A disease of the lower motor neurons that affects the gray matter of the spinal cord, specifically the central horns. In a retrospective study, spinal cord segments from all patients who had had poliomyelitis showed loss or atrophy of motor neurons, severe reactive gliosis, and a perivascular and intraparenchymal inflammation even in the chronic phase, up to 20 years after infection. In acute to subacute phase (up to 8 weeks after acute illness), the ventral horn cells are characterized by a severe inflammation, neuronophagia, active gliosis, and destruction of the anterior horn cells. This correlates with the T2 signal hyperintensity in the region of the ventral horns on MRI and should be fairly specific for poliomyelitis.
(Reference : Poliomyelitis: Hyperintensity of the Anterior Horn Cells on MR Images of the Spinal Cord; Mark S. 1 Jeffrey M, Charlene A. Tate, Vladislav Zayas, and J. Donald Easton)

5. Compressive myelopathy 
A bulging disc causing mechanical compression over redicular artery leading to a chronic ischemic changes and Gliosis in the region of anterior horn cell. Disc herniation and degree of canal stenosis may be not be severe as here main culprit is radicular artery compression which is lying anterior to cord and not the direct cord compression by disc.

6. Hopkins syndrome
Flaccid paralysis of one or more limbs, 4 to 7 days after an asthma attack. Anterior cord lesions in 2 to 12 year-old children with onset over 1 to 2 days are followed by permanent paralysis. CSF typically contains 20 lymphocytes and 20 polymorphonuclear neutrophils (Hopkins 1974).

7. Radiation myelopathy
Possible with an exposure over 50 Gy. Damage is delayed up to 15 years after exposure but is typically 10 to 16 weeks later (Yamada et al 1987). Radiation myelopathy causes vasculopathic and sometimes anterior horn cell changes with high MRI T2 signal owing to Gliosis in corresponding region on follow up studies. 

Purely Intracanalicular Acoustic Schwannoma MRI

MRI Brain FIESTA (3D CISS) sequence shows an intra canalicular nodular low signal intensity of a 8th CN Schwannoma confined to Internal Auditory Canal on left side.

Comparison of FIESTA and Contrast enhanced study in MRI screening for Acoustic Schwannoma

Acoustic schwannomas are a treatable cause of sensorineural hearing loss.
Currently, MRI is the gold standard examination and screening test for exclusion of acoustic schwannoma particularly those confined to internal auditory canal.

In MRI we have two main options  in addition to the routine MRI sequences, one is Contrast Enhanced study and second is FIESTA (fast imaging employing steady-state acquisition) sequence.
Contrast Enhanced study consist of plain T1 and Gadolinium-enhanced T1-weighted images, both in multiple planes, adds extra time and cost to the examination, and possibility of contrast reaction exists.
Whereas FIESTA is a single sequence, a true-FISP (free induction steady-state precession) sequence that provides high-resolution fluid-bright images of the CPAs and basal cisterns.

In a study of 50 patients, results of contrast enhanced study and FIESTA images were compared. The hypothesis was that the FIESTA sequence can replace contrast enhanced study for screening and diagnosis of AS confined to internal auditory canal. The results showed that in 98% of cases, this was possible. So the FIESTA sequence can be employed in isolation for screening of AS. Same can be equally beneficial in cases where gadolinium is contraindicated such as pregnancy. However, Contrast enhanced study should be employed when pathology is seen and to follow-up post-surgical patients.

Conclusion: Use of the FIESTA (CISS) is sufficient to exclude AS confined to internal auditory canal without the need for gadolinium-enhanced sequences. 

Reference : Comparison of FIESTA and gadolinium-enhanced T1-weighted sequences in magnetic resonance of acoustic schwannoma; Paul J. Rigby

Measles Encephalitis MRI

 A 12 years old patient with characteristic morbiliform rash.

Admitted in our neuro institute with symptoms of encephalitis occurred 10 days after appearance of the rash, altered sensorial with lower limb flaccid paralysis now.

Csf report positive for specific IgM and IgG antibodies.  

Clinical diagnosis was measles encephalitis.

Here is her on admission MRI Brain Axial FLAIR, T2w and Diffusion. 

MRI Brain Axial FLAIR shows confluent bilateral cerebral white matter hyper intensity extending along external capsules with faint restricted diffusion. T2 w images show bilateral basal ganglionic  symmetric T2 hyper intensity with focal parenchymal swelling consistent with clinical diagnosis of measles encephalitis.

Imaging findings of Measles Encephalitis mentioned in literatures are 1. Multifocal high signal in bilateral cerebral hemispheres, swelling of the cortex, 2.  Bilateral, symmetrical involvement of the putamen and caudate nucleus, lesions showing low apparent diffusion coefficients. 3. Sub acute gyriform hemorrhage, asymmetrical gyriform contrast enhancement mentioned in severe cases. 4 Diffuse cerebral cortical atrophy, gliosis and encephalomalacic changes on follow up MRI studies. 

Histopathological findings of Measles Encephalitis mentioned in literatures are perivascular mononuclear cell infiltration, white matter demyelination, gliosis and intranuclear and intracytoplasmic eosinophilic inclusions in neuronal and glial cells in the temporal, parietal and occipital cortex as well as in the thalamus. 

Slit Ventricle Syndrome

• Slit ventricle syndrome occurs in minority of patients who have been shunted.
• "Slit ventricle" refers to finding of very small ("slit-like") ventricles on CT or MRI indicating excessive drainage.

Diagnostic criteria: 
An association of  clinical signs of headache, vomiting with signs of  slit like ventricles on CT or MRI. 

• Headache may be intermittent, often postural occurring when standing up and resolving when the patient lies down. Vomiting can be related to visual or auditory disturbance, drowsiness.
• Symptoms usually present years after shunt placement or shunt revision.
• Severe form of slit ventricle syndrome occurs in children. The absence of cerebrospinal fluid (CSF) within the ventricles combined with a growing brain leads to situation in which "the brain is too big for the skull." The intracranial pressure (brain pressure) can be very high. Adults can develop a milder form of slit ventricle syndrome. 
• The diagnosis of slit ventricle syndrome can be difficult and the condition is often misdiagnosed or the diagnosis delayed. The finding of small ventricles in a shunted patient can be misinterpreted as a properly working shunt. Most patients with small ventricles on CT or MRI may not have the slit ventricle syndrome clinically. Patients must be symptomatic to call Slit ventricle Syndrome. 
• Typically, the shunt is nearly blocked but still barely flowing.

A case of  Vp shunt done for Post TB Meningitis Hydrocephalus. Now came for follow up with new onset of headache and nausea. CT Brain plain shows right parietal Vp shunt with collapsed lateral ventricles. Possibility of "Slit Ventricle Syndrome" considered clinically and patient re admitted for further management.  

Treatment: 
The management of slit ventricle syndrome is difficult and challenging.
In general, a neurosurgeon with expertise in the management of hydrocephalus is optimal.
Various treatment options have been proposed, and include:
1. Observation.
Usually limited to minimally symptomatic patients
2. Anti-migraine medicines.
3. Shunt revision.
 Change the ventricular catheter.
 Change the shunt valve.
 Add siphon controlling device (SCD).
 Programmable valve with or without SCD.
 Converting to a lumboperitoneal shunt.
4. Temporarily blocking the flow of the shunt (via "externalization" of the shunt) in order to expand the ventricles.
This should be done with ICP monitoring due to the risk of coma.
Many patients have aqueductal stenosis, and therefore are candidates for endoscopic third ventriculostomy (ETV).
In some cases, a special shunt configuration draining both the ventricles and the cisterns (space around the brain) can equalize the inner and outer brain pressures, thus reducing the chance of producing slit ventricles again. This type of shunt is called a ventriculocisternoperitoneal shunt.
5. Subtemporal decompression.
This procedure is rarely performed because improvements, if any, are typically short-lived.

HELLP Syndrome with Spontaneous subdural haematoma and intracerebral haemorrhage

A 32-year old primigravida,with prolonged labour and fetal distress, fell unconscious during labour.

Refereed to our neuro institute for further investigation and management. 

No history of trauma. 

On admission MRI Brain shows:

Left fronto parietal subdural haematoma with max with 13mm, T1 bright signals of hematoma attributed to Meth Hb – a sub acute stage blood degradation product.

An associated left frontal intracerebral hematoma. 

Significant mass effect, mid line shift with internal herniation. 

MR Angiography of Brain normal. No obvious aneurysm. 

No abnormal adjacent T2 flow voids to suggest any vascular malformation.

MR Venography of Brain normal, particularly superior sagittal sinus. 

No obvious cortical vein thrombosis on GRE. 

Patient underwent emergency decompressive craniotomy.

Follow up CT shows:

Left anterior craniotomy with evacuation of left fronto parietal subdural hematoma and left frontal intra parenchymal bleed.
Complete reversal of mass effect and mid line shift. No mid brain compression.
Bilateral frontal subdural pneumocephalus noted, which also regressed on subsequent follow studies. 

Patient is clinically improving, residual right hemiparesis. 

During this a diagnosis of HELLP syndrome with Disseminated Intravascular Coagulation (DIC) was made, as her Platelet count was 50,000/μL (low), e/o hemolysis on peripheral blood smear with Serum lactate dehydrogenase : 800 IU/L (Abnormal) and Serum aspartate aminotransferase : 80 IU/L (Abnormal)

HELLP (haemolysis, elevated liver enzymes, and low platelet count) syndrome can result in a fatal intracranial haemorrhage during the perinatal period. 

Patients with HELLP syndrome should be managed as high-risk, which requires an excellent working relationship of the physicians involved. Prompt recognition of intracranial haemorrhagic complications and neurosurgical intervention are particularly important.

CSF shunt imaging

CSF, Cerebrospinal fluid is an ultra-filtrate of plasma, produced by the choroid plexus of the lateral ventricle, fourth ventricle and ependymal lining of the ventricles.
CSF flows from the lateral ventricle through the foramen of Monro into the third ventricle and then into the fourth ventricle through aqueduct.
The CSF exits the ventricular system via the foramina of Luschka (lateral) and Magendie (medial) situated in the fourth ventricle. CSF then ascends into the basal cisterns and around the cerebral convexities where it is reabsorbed by the arachnoid villi which project into the dural venous sinuses.

Hydrocephalus is defined as excess of CSF, primarily caused by obstruction to the flow of CSF within the ventricular system.

Hydrocephalus is primarily classified into two types: communicating and noncommunicating.

Communicating or extraventricular hydrocephalus is caused by extraventricular obstruction at the level of the arachnoid villi and decreased absorption of the CSF mainly caused by prior hemorrhage, meningitis or obstruction of the dural venous sinuses. On imaging lateral ventricles, third ventricles as well as fourth ventricle are equally dilated as level of obstruction is after fourth ventricle.

Non communicating or intraventricular hydrocephalus is induced by obstructive lesions at various levels within the ventricular system due to various causes such as intra ventricular tumors or aqueductal stenosis. Here dilatation is confined to ventricular system proximal to the level of obstruction.

An intra ventricular mass in third ventricle causing non communicating hydrocephalus.
Fourth ventricle is not dilated. 

Csf Diversionary shunts

CSF diversionary procedures like shunt placement are one of the most common pediatric neurosurgical procedures.

Types of shunt include:
ventriculoperitoneal (VP),
ventriculopleural (VPL),
ventriculoatrial (VA),
ventriculolumbar (VL),
ventriculovenous and
Ventriculo-gallbladder.

TheVP shunt is by far the commonest type of shunt used in the pediatric population.
The ventriculolumbar shunts are mainly reserved for adults with normal pressure hydrocephalus and patients with small slit ventricles or recurrent VP shunt malfunction.
Ventriculoatrial shunts have the distal tip in the right atrium. Complications like sepsis, thromboembolic events, shunt nephritis and pulmonary hypertension have led to the decline of their use except as a last resort. Ventriculopleural shunts are also not favored due to inadvertent life-threatening complications like pneumothorax, pleural effusion and infection.
Other proposed shunts have also failed due to various complications and are rarely used in clinical practice.

Ventriculoperitoneal (VP) shunt

Shunt tube has a proximal intracranial segment inserted through the frontal, parietal or temporal bone, so that the tip and the side holes of the catheter lie within the frontal horn of the lateral ventricle.
Care is taken by the neurosurgeons to avoid proximity of the shunt catheter tip to the choroid plexus, to prevent the occlusion of the catheter by the growth of choroid plexus into the tip and side holes of the shunt catheter. The distal tip of the catheter is tunneled through the skin of the neck, thorax and abdomen into the peritoneal cavity for the drainage of CSF.
Today neurosurgeons have a wide variety of shunts with programmable valves to choose from for a particular patient.
One of the commonly used valves is the Codman Hakim programmable valve which has 18 pressure settings ranging between 30 and 200mmH2O.
The neurosurgeon selects one of the settings at the time of shunt placement and is also able to make precise pressure adjustments to help control intracranial pressure and the ventricle size at any time in the future.

Shunt imaging 

Normal findings
In patients with previous ventricular shunt, the most common and normal finding is an area of Gliosis in the brain along the course of shunt tube (See image)
Diffuse and relatively thin pachymeningeal enhancement along the inner table of the skull and in the dural reflections is a normal finding on post shunt post contrast T1 w MRI images, due to the continued use of the ventricular shunt.
Post shunt Ventricular asymmetry is a known and common finding after ventricular shunting. Asymmetry result due to significantly greater decrease in ventricular size on the side of the ventricular shunt catheter and isolation of the contra lateral ventricle from adequate decompression. Studies have shown that contra lateral placement of tip catheter after perforation of the septum pellucidum that is transeptal placement of catheter would significantly decrease the incidence of post shunting ventricular asymmetry. A special cathter is used which consist of two sets of holes, such that holes are located in both the lateral ventricles. (See Image)

A linear area of Gliosis in right parietal region along the course of shunt tube.

Post shunt mild asymmetry of lateral ventricles, left lateral ventricle wider than right

Shunt malfunction
If a child with a shunt presents acutely with the classical clinical triad of raised ICP with headaches, vomiting and papilledema is need evaluation of shunt for any malfunction.

Causes of shunt malfunction
Mechanical causes leading to inadequate drainage:
○Kinking
○Discontinuity/disconnection
○Break/fracture
○Functional failure of the valve/shunt apparatus
○Migration
Overdrainage:
○Epidural, subdural and intracranial hematoma
○Slit ventricle syndrome
Infection:


INTRACRANIAL COMPLICATIONS

1. Shunt infection.The prevalence of shunt infection is reported in 2.6%-38% of cases. Most infections develop within 2 months from the shunt placement. The common microorganisms are Staphylococcus aureus, Staphylococcus epidermidis, or gram-negative enteric infections.
E/o Ventriculitis and meningitis on CT and MR imaging, are ventriculomegaly, an abnormal enhancement along ventricular ependymal lining and or cerebral cortical sulci. Shunt replacement is usually necessary.
Repeated infections can lead to cerebral venous sinus thrombosis.

2. Shunt obstruction can occur at any time after insertion, and all points along the shunt course. Presents with clinical evidence of raised intracranial pressure.
There two most common locations for obstruction, one is ventricular catheter tip, which can be blocked by ingrowth of choroid plexus, and second is shunt valve, where blood or debris can block the lumen of the valve.
If the ventricular catheter is obstructed by ingrowth of choroid plexus into the lumen of the ventricular catheter tip, its removal is complicated by the risk of bleeding caused by avulsion of choroid plexus if the catheter is forcefully removed.

3. Overdrainage refers to when shunt removes more fluid than necessary for that particular patient. Early rapid reduction in ventricular size may result in collapse of the brain and accumulation of extra-axial fluid or results in mid brain compression.
* Slit ventricle syndrome, CT will reveal collapsed converging lateral ventricles (see image)
* Paradoxical herniation and sunken skin flap, very uncommon complication, seen in patients with a large craniectomy defect who then undergo CSF drainage by either lumbar puncture or ventriculoperitoneal shunt result in marked decrease in Csf pressure, which leads to reduction in intracranial pressure making intra cranial content vulnerable to atmospheric pressure. This pressure imbalance particularly the negative intara cranial pressure deforms brain and mid line.
On CT / MR Imaging a significant mid line shift away from the craniectomy side with subfalcine and or transtentorial herniations. Uncal herniation if severe may results in mid brain compression. (see image)
Clinically patient present with depressed level of consciousness, autonomic instability, signs of brainstem release, and focal neurologic deficits.
Management: Paradoxical herniation is a neurosurgical emergency and urgent treatment is necessary in order to increase intracranial pressure, to stop any CSF leakage, and restore the continuity of the calvaria.
Options include urgent placing the patient in Trendelenburg position and head inclined towards to craniectomy side, clamping ventricular shunts or drains, administering intravenous fluid. Cranioplasty as soon as possible. Paradoxical herniation also has been reported to be effectively and quickly reversed with a lumbar epidural blood patch or clamping ventricular shunt tube.

Slit ventricle syndrome

Sunken Skin flap with Paradoxical herniation

EXTRA CRANIAL COMPLICATIONS

1. Abdominal pseudocyst, a pseudocyst is a loculated intra-abdominal fluid collection that develops around the peritoneum and is more common than ascites.
Indicates the presence of a chronic low-grade infection; however, it is common to find sterile fluid within the pseudocyst cavity when it is aspirated.
Symptoms may be consistent with bowel obstruction if the pseudocyst is large.

2. Shunt misplacement can also occur at the distal end of the catheter, including the abdomen, atrium, or pleura. Patients present with abdominal discomfort and eventually may develop headache, nausea, or vomiting. CT scan may discloses, the distal end of the shunt located in the preperitoneal space, resulting in fluid collection under the abdominal incision.

3. Broken shunt. The typical presentation is usually many years after initial insertion and is related to both biomechanical stress as patient's height increases and the inherent degradation of indwelling components because of host reactions. The distal tubing should be free to slide in the subcutaneous tract; however, scar tissue may tether the tubing and produce shear forces that promote fractures as the children grows. The common presentation is that of mildly elevated raised intracranial pressure. It is also common for patients to present with pain, mild erythema, or swelling over the shunt tract often in a location over the shunt fracture.
Shunt series comprising of AP and lateral radiographs of the skull and neck, radiographs of the chest and abdomen are obtained to evaluate for obvious kinks, discontinuity or disconnection. The commonest site of disconnection is between the valve apparatus and the distal shunt tubing.
Most shunts have translucent areas that one should be aware of to avoid being mistaken for abnormal disconnection.
CT scan of the brain is mainly done to assess the size of the ventricles. Worsening hydrocephalus and overdrainage with epidural, subdural and intraventricular hematomas and slit ventricles are easily identified on a CT brain study.

As mentioned earlier, the programmable valves are susceptible to magnetic disturbances due to their ferromagnetic properties, and hence evaluation of valve pressure is necessary after a diagnostic MRI.