Sunday, 24 May 2015

Role of MR Csf flow study in NPH

By definition NPH is Ventriculomegaly on MRI with normal CSF pressure, altered CSF dynamics.

Of course NPH is a clinical diagnosis.
The classical clinical triad of NPH is
1) urinary incontinence
2 ) deterioration in cognition (dementia) and
3 ) Ataxia i.e. Gait disturbances.
As the name suggests mean CSF opening pressure in patients with NPH is within the normal range with a classic neurological sign is magnetic gait.

Best diagnostic clue on MRI is ventricles and Sylvian fissures symmetrically dilated out of proportion to sulcal enlargement, with normal hippocampus which distinguishes NPH from atrophy.
Ventriculomegaly is prominent in all 3 horns of lateral ventricles and 3rd ventricle, with relative sparing of 4th ventricle.

Role of MRI is now not confined only to support the clinical diagnosis of NPH but is to identify shunt-responsive NPH pts from non responsive by calculating aqueductal stroke volume non invasively.
This is because studies have shown that aqueductal stroke volume in patients of NPH decreases later in the disease process despite clinical progression and classifcal findings on MRI this has been theorized to be caused by cerebral atrophy, which indicates that the patient is unlikely to respond to shunt surgery.


Normal CSF flow and its dynamics

The stroke volume across aqueduct is the average CSF volume flowing through the aqueduct in one cardiac cycle, craniocaudad during systole OR caudocraniad during diastole.
Normal values of stroke volume is < .04 ml/cycle
It is assumed that the net flow over 1 cardiac cycle is [negligible enough to be considered as] zero
Aqueductal velocity (caudal): 3-8mm/s
The peak velocity was determined from the maximum value of the measured velocities of each cardiac phase.


CSF flow study findings in NPH
In NPH actually there is lack of flow from the cisternal and subarachnoid spaces with significant increase in amount of ventricular csf flow.
There increased flow void across aqueduct with increase stroke volume.
1) Increased aqueductal stroke volume is the average volume of CSF moving through the cerebral aqueduct calculated by summing the absolute values of stroke volume in systole and diastole and dividing by 2
i.e   Forward stroke volume +  Reverse stroke volume   /   2
2) Increased aqueductal peak velocity.

Various publications have set various normal and abnormal ranges.
Flow rate of > 24.5mL/min 95% specific for NPH.
Stroke volume of > 42 microL shown on one paper to predict good response from shunting was statistically significant (P < .05).Studies have shown that aqueductal stroke volume decreases later in the disease process despite clinical progression.
Sroke volume upper limit is now suggested to be variable between institutions due to intrinsic scanner differences, thus each centre should obtain their own "normal values", with the upper limit being suggested as two times the normal value.
There was no statistically significant relationship between aqueductal CSF flow void score and responsiveness to shunting.

Case 1

With clinical diagnosis of NPH

MR brain reveals diffuse cerebral and cerebellar cortical atrophy.
The ventricular dilatation is disproportionate to the amount of cortical atrophy, scalloping of inferior margin of corpus callosum and prominent flow void in posterior portion of third ventricle, across cerebral aqueduct and superior portion of fourth ventricle consistant with clinical diagnosis of NPH.
Csf flow study report :
Gated cine phase contrast study was performed to evaluate the CSF flow.
The diastolic phases are equal in number to the systolic.
The stroke volume is 41 microliters per cycle consistent with shunt responsive status (Reference : Patients with stroke volume more than 40 microliters respond well to VP shunt _ Bradley et al)

Case 2 

Atrophy Vs NPH clinically

MRI brain reveals moderate cerebral and cerebellar atrophy. The ventricular dilatation is mildly disproportionate to the amount of cortical atrophy.

Csf flow study report :
Gated cine phase contrast study was performed to evaluate the CSF flow.
The diastolic phases are equal in number to the systolic. The stroke volume is 30 microliters per cycle consistent with non-shunt responsive status. ( Reference : Patients with stroke volume more than 40 microliters respond well to VP shunt _ Bradley et al).

Contributors:
Dr Deepak Patkar (HOD, Nanawati Superspeciality Hospital, Vile Parle, Mumbai)
Dr Balaji Anvekar (Short visiting Fellowship in Neuroradiology and Recent Advances in Neuroimaging)

Friday, 15 May 2015

Syntelencephaly MRI

A 14 yo male child, birth history uneventful.Complaints multiple episodes of seizures since 10 months with history of developmental delay and clinical impression of cerebral palsy with epilepsy

On MRI, 
The interhemispheric fissure not visualized in fronto parietal region with midline fusion of the cerebral hemispheres, single lateral ventricle cavity. 
The sylvian fissure extending across the midline. Body of corpus callosum is deficient. 
Normal 3rd and 4th ventricle.
The fused superior frontal cortex is thick , has a agyric / polymicrogyric  pattern.

Diagnosis : Syntelencephaly.

A varient of semilobar holoprosencephaly _ Congenital malformation of brain also known as Middle Interhemisheric variant.
A rare malformation in which the cerebral hemisphere fails to divide in the posterior frontal and parietal region.

Similar case : Semi-lobar-holoprosencephaly

Contributed by Dr Mitusha Verma SR DNB Radiology Nanavati. 

Thursday, 14 May 2015

Haemorrhagic encephalitis - CNS Leptospirosis MRI

41 y o male patient admitted with c/o bilateral Lower limb Pain, Fever and Rapidly falling platelets.
Lab Investigations on admission Hb- 11.0, Platelets - 20,000 , Creatinine - 2.5, Bil(T)- 3.7, SGOT - 185, LDH- 1570

MRI Brain

Axial T1 and T2w images:
Axial GRE images:
DW images:
Sagittal T2wi for pituitary:

MRI shows multiple, patchy T2 hyperintense lesions of varying sizes on Flair and T2 W images in bilateral cerebral parenchyma involving the cortex and sub cortical white matter.
Some of the lesions show hyperintense foci on T1 weighted images, which appear hypointense on T2 weighted images and bloom on gradient echo images representing hemorrhage.
Restricted diffusion along the pyramidal tracts from the corona radiata upto the pons. These lesions are symmetric. Similar changes are seen in the corpus callosum, especially in the genu and splenium.
The pituitary gland appears hyperintense on T1 weighted images and hypointense on T2 weighted images and is probably also involved.

Findings are suggestive of haemorrhagic encephalitis. It involves cerebral hemispheres, corpus callosum and brain stem, as described.
The middle cerebellar peduncles and pituitary gland are also involved.

Follow up lab investigations shows raising Creatinine to 6.9,  Platelets on lower side.
Dengue NS1Ag -negative, Chikungunya IgM- Negetive, Leptospira IgM positive, Malaria -ve.

Final diagnosis : 

Haemorrhagic encephalitis - CNS Leptospirosis

Discussion: 

Hemorrhagic fevers are febrile illnesses with abnormal vascular regulation and vascular damage. Although the combination of fever and hemorrhage can be caused by a number of human pathogens: viruses, rickettsiae, bacteria, protozoa, and fungi, the term hemorrhagic fever usually refers
to a group of illnesses that are caused by 4 different families of
viruses: Arenaviridae, Filoviridae, Bunyaviridae, and Flaviviridae

Classic hemorrhagic fever with renal syndrome is a syndrome characterized by sequential periods of fever, hypotension, oliguria, and diuresis.

Headache may be associated with aseptic cerebral edema, or CNS hemorrhage .
Brainstem or posterior fossa subarachnoid hemorrhages are found.
May be associated with Pituitary dysfunction with pituitary apoplexy or panhypopituitarism

Leptospirosis

Infection caused by bacteria of the Leptospira type.
Symptoms - none to mild such as headaches, muscle pains, and fevers.
The disease presents with variable combinations of clinical syndromes, which cause diagnostic confusion.
In most cases hemorrhage in Leptospirosis occurs in the pulmonary and GI system and not in the Central Nervous system.
A small proportion of patients develop severe icteric illness with renal failure- Weils Disease.
Marked elevations of bilirubin with mildly elevated transaminases are some
characteristic features of leptospirosis.

Spectrum of CNS Leptospirosis

Aseptic Meningitis - most common
Rarely encephalitis , cerebellitis , myelitis.
Intracranial hemorrhage is a rare and serious presentation of leptospirosis.
Peripheral Nervous System - Polyneuritis.
Other associations- GBS , Stroke.

Contributed by Dr Mitusha Verma SR DNB Radiology Nanavati. 

Monday, 11 May 2015

Understanding Primary Dystonia with Advanced MRI Sequences

A 13 year old male patient resident of UK came with complaints of Dystonic hand movements on activity, right more than Left.
No history of seizures. No obvious cognitive impairment. No prior investigations were done.

Routine MRI brain imaging


Conventional MRI Brain normal 

Arterial Spin Labelled Perfusion MRI images of Brain


What is Arterial Spin Labelled Perfusion MRI ? 
Uses magnetically labelled endogenous blood  water. 
Ideal in  brain as the arterial supply is  well defined &  perfusion to brain tissue is high.
Higher magnet strengths give improved ASL
Gives an idea of tissue perfusion without using contrast
Estimates cerebral blood flow in ml/gm/min






Diffusion Tensor Imaging and Fibre Tracking images of Brain



What is Diffusion Tensor Imaging ? 
A form of diffusion-weighted imaging
Analyzes the microstructural integrity of white matter
Fractional anisotropy -The major index for this discrepant diffusion 
Higher FA values correlate with more ordered tissue containing a larger number of aligned axons
Higher FA values reflect tissue integrity and coherence


Fractional Anisotropy Maps


Average fractional Anisotropy ( FA) values:

Putamen                      (Right) 0.293             (Left) 0.328
Posterior limb of IC    (Right) 0.616             (Left) 0.709
Genu of IC                  (Right) 0.693             (Left) 0.637
Corpus callosum         (Right) 0.697             (Left) 0.880
Thalamus                    (Right) 0310              (Left) 0.321

Thalamo cortical tract fibers appear relatively sparse on right side compared to left.
Corpus callosal and cortico spinal tract fibres appears more ore less symmetrical on both sides.

Interpretation:

Average fractional Anisotropy values are more in putamen, Posterior limb of left internal capsule, Corpus callosum and left thalamus.
In the genu of internal capsules, the values are greater on right side.

Segmented Brain Volumes

Volumetry was performed using 3DSPGR acquisition.
Whole brain and segmented brain volumes were calculated.


Left putaminal volume is approximately 13 % more than right.

MR Spectroscopy

To summarize the findings in this case..
Structural MRI is normal.
MR spectroscopy is normal.
Arterial Spin Labelled MR Perfusion (ASL) show increased cerebral blood flow in left parietal cortex and caudate nuclei.
DTI and FA maps show Relatively dense Thalamo cortical tracts on left.
Segmented Brain Volume show 13 % increased putamen volume on left.

Review of Literature:

Primary Dystonias is a hyperkinetic movement disorder characterized by involuntary, repetitive twisting movements.
Early onset - prior to 26 years of age.
Associated with a known gene carrier status (e.g., DYT1).
Symptoms more likely  begin in  one extremity and have a tendency to be generalized.

Conventional MRI does not typically reveal brain abnormalities.



Segmented Brain Volumes
Putamen has been predominantly involved in focal hand dystonias.
The involved side show > 10% increase in putaminal volume.
Other areas which may be involved are thalami and caudate nucleus.


Summarization of Literature…
Gray matter changes are not restricted to the basal ganglia.
Sensorimotor cortices, thalamus, and cerebellum may also be involved
White matter aberrations mainly involve cortico-striato-pallido-thalamic and cerebello-thalamo-cortical pathways.
Whether these changes are causative or compensatory remains unknown.
Newer MRI sequences may provide an insight in understanding disease pathophysiology and intricate brain networks involved.

To conclude…
Advanced MRI sequences like ASL, DTI, Segmented brain volumes may provide more comprehensive insight into pathophysiology of dystonia.
Further studies in this regard are needed to understand these findings and link them to disorder-specific clinico-behavioral characteristics.

References:
Newer advances in the pathophysiology of focal dystonias  Brain (2006), 129, 6–7
Thalamocortical Connectivity Correlates with Phenotypic Variability in Dystonia; May 2014 An Vo1,Wataru Sako1, Martin Niethammer1, Maren Carbon
Primary Dystonia: Conceptualizing the Disorder Through a Structural Brain Imaging Lens  Ritesh A. Ramdhani & Kristina Simonyan
Cortical somatosensory reorganization in children with spastic cerebral palsy: a multimodal neuroimaging study Front. Hum. Neurosci., 12 September 2014 Christos Papadelis1,2*†, Banu Ahtam1,2†, Maria Nazarova

Contributors:
Dr.Deepak Patkar (HOD Radiology) Nanavati Superspeciality Hospital, Mumbai
Dr.Mitusha Verma SR DNB Radiology Nanavati. 

MR Perfusion Imaging in Recurrence of Neoplasm with Subependymal spread : A Case Report

A fifty seven years old man, operated case of left parieto-temporal glioblastoma multiforme, post chemotherapy and post radiotherapy status.

Protocol:

Scan done on GE DISCOVERY 750 W 3 T scanner after injecting 10 ml of Dotarem.
Pre and post contrast MRI of the brain was performed using T1 and T2 weighted sequences in multiple planes, using a quadrature head coil. Perfusion studies of the brain were performed after intravenous injection of Dotarem using EPI sequences. Negative enhancement integral was evaluated. ROIs were placed within different parts of the lesion and normal appearing contralateral parenchyma and time intensity curves were plotted.
Single and multi voxel spectroscopy and chemical shift imaging were performed through the lesion using short TE (35 ms) PRESS sequences. Post processing was performed using FUNCTOOL on ADVANTAGE GE workstation.

Findings :

There is a large ill-defined, mixed signal intensity lesion in left parietotemproal region.  Multiple areas of blooming are seen within, suggestive of hemorrhagic changes.  Areas of restricted diffusion are also seen within the lesion which correspond to infarcts, likely treatment induced. Heterogeneous post-contrast enhancement is detected with non-enhancing areas representing necrosis.

These findings are suggestive of post-treatment changes admixed with residual neoplasm in left temporo-parietal region. Diffuse subependymal enhancement is detected along both lateral and third ventricles, suggestive of subependymal spread of neoplasm.

Single voxel spectroscopy from the enhancing component of the lesion showed . elevated choline and reduced NAA peak, along with elevated lactate levels. Cho / Cr ratio is 1.531 and Cho / NAA ratio is 4.529.

Multivoxel spectroscopy of necrotic areas reveal elevated lactate peak and diminished choline and NAA peaks suggestive of post radiation change.

The enhancing areas show increased perfusion with maximum rCBV ratio (calculated from signal intensity value) of 2.8.  The right subependymal areas of enhancement also demonstrate hyper perfusion with rCBV ratio calculated from signal intensity value) of 3 suggestive of high grade neoplastic infiltration.
The necrotic areas are hypoperfused.

Diagnosis:

Post treatment recurrence of neoplasm with sub ependymal spread.

CE - MRI, Dynamic susceptibility contrast MRI and MRS increase the diagnostic confidence of detecting tumor recurrence in a treated case of glioblastoma multiforme.

Contributors:

Dr. Deepak P. Patkar (HOD) Nanawati Superspeciality Hospital, Mumbai
Dr. Amit J. Choudhari Consultant Radiologist, Nanawati Superspeciality Hospital, Mumbai
Dr Balaji Anvekar

Wednesday, 15 April 2015

Frontal subcortical white matter cystic lesions MRI

A 30 y o male with headache.
MRI Brain with contrast shows:






Multiple T2 hyper intense well defined cystic foci in right frontal sub cortical white matter.
Lesions are iso intense to Csf on all pulse sequences.
No abnormal enhancement on post contrast T1.
No obvious restricted diffusion or hemosiderin staining on GRE in corresponding region.
No significant mass effect.
No adjacent white matter Gliosis.
No obvious calcification on CT sections.
Rest of the MRI brain within normal limits.

These appears to be benign lesions, and incidental finding not related to patient's headache.
Possibility given was Enlarged peri vascular spaces ( ' V R Spaces') and advised EEG correlation.
EEG was unremarkable.

Follow up imaging after 6 month revealed no change which again favors imaging diagnosis of Enlarged peri vascular spaces.

Bilateral Hypertrophic Olivary Degeneration MRI

A 50 y o was admitted after acute onset of unconsciousness. On admission MRI brain reveled hypertensive Pontine bleed extending in adjacent mid brain. His clinical condition gradually improved.

On follow up after 6 month pt was alert, dysartric, bilateral dysmetria of the arms without paresis, bilateral horizzontal gaze paresis. No palatal myoclonus.

During this 6mth follow, MRI  shows;
A resolved chronic Pontine bleed with,
New bilateral and symmetric T2 hyper intense foci with mild swelling in the region of inferior olivary nuclei of medulla suggestive of bilateral hypertrophic inferior olivary degeneration. 

Hypertrophic olivary degeneration ( HOD)

Hypertrophic olivary degeneration is a rare finding secondary to focal lesions of the brain stem involving Guillain–Mollaret triangle.

The three corners of the triangle are:
1.             Red nucleus.
2.             Inferior olivary nucleus
3.             Contralateral dentate nucleus.

In CNS the degeneration of an anatomical structure is usually characterized by neuronal loss replaced by proliferation of glial elements.
Unique to the inferior olivary nucleus is transneuronal degeneration resulting in hypertrophy.
Clinical presentation is Palatal myoclonus, a classically described feature.
Interruption of either of the connections between the dentate nucleus and contralateral red nucleus (dentatorubral tract, superior cerebellar peduncle) or the connection between the red nucleus and ipsilateral inferior olivary nucleus (central tegmental tract) leads to changes in the olive.
In short hypertrophic olivary degeneration can be caused by any lesion involving the above mentioned structures, it is typically seen with focal lesions involving the ipsilateral central tegmental tract, the contralateral superior cerebellar peduncle, or the dentate nucleus.
Isolated lesions of the inferior cerebellar peduncle do not cause HOD, as anatommically there are no direct connections between the inferior olivary nucleus and the contralateral dentate nucleus.

Pathologically, cell body enlargement, vacuolation of the cytoplasm, astrocytic hyperplasia and proliferation, demyelination, and fibrillary gliosis have been described.

Hypertensive bleeding is a relatively common cause of pontine haemorrhages resulting in hypertrophic olivary degeneration.

Imaging wise the inferior olivary nucleus or nuclei gets larger and increases in T2 signal intensity. Typically, within a few months T2 signal increases and lasts 3-4 years, whereas hypertrophy occurs later (at about one year), and resolves by 3-4 years.
On imaging DDs include infarction, demyelination, Neoplastic, metastases, lymphoma, infection, including tuberculoma.

T2 hyperintense non enhancing lesion that is accompanied by enlargement of the olivary nucleus, particularly if bilateral and symmetric, as our patient, can be explained only by hypertrophic olivary degeneration. Typically T 2  hyperintensity is evident on follow up imaging  the signal abnormality was absent in the on admission MR imaging. In the next few months the patient could complain palatal myoclonus which is not evident now.

Most commonly a lesion involving central tegmental tract causes unilateral olivary degeneration. Our patient is having bilateral hypertrophic degeneration from lesion located in the midbrain and Pons.

Sunday, 5 April 2015

MELAS

A 15 y o male with altered sensorium. 

Here is CT Brain study. 


CT study of Brain shows bilateral symmetric chronic lacunes in bilateral caudate nuclei.
Rest of the CT brain normal.
No associated atrophy or cortical involvement.

I really got surprised when I noted the clinical history.
Patient was a known case of MELAS, laboratory Studies with abnormal reports of Serum lactic acid, serum pyruvic acid, cerebrospinal fluid (CSF) lactic acid, and CSF pyruvic acid noted.

Imaging findings are actually atypical for MELAS.

The typical radiographic features of MELAS includes multiple acute and chronic infarcts in multiple vascular territories, may be either symmetrical or asymmetrical. Parieto-occipital and parieto-temporal involvement is most common. Associated basal ganglial calcification and atrophy.

MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) is one of many mitochondrial disorders, only inherited from the mother, characterised by 'stroke-like' episodes, typically in childhood or early adulthood. 90% present before 40 years of age.
Clinical presentation usually has a relapsing remitting course with or without superimposed accretion of permanent deficits.
Clinical presentation is characterized by stroke like episodes, encephalopathy, seizures, dementia, lactic acidosis, muscle weakness, deafness. 

Astrocytoma vs Ependymoma

These common spinal cord neoplasms, differentiating Astrocytoma vs Ependymoma imaging wise is challenging, sure differentiation is out of imaging consensus however the combination of following set of findings can be used to give a more likely possibility of one over other.
Again it is one of favorite questions in FRCR 2A.

Astrocytomas are common in Children, Thoracic region, Eccentric lesion in spinal cord, Ill defined margins, Long segment involvement , No to faint enhancement on post contrast. 

Ependymomas are common in Adult, Cervical region, Central location in spinal cord, Well defined margins, Short segment involvement of cord, Avid enhancement on post contrast, Associated with cord syrinx, intralesional Bleed and Spinal canal remodeling.  

Cholesteatoma vs Cholesterol Granuloma


This is one of favorite questions in FRCR 2A exam.