Hyperdense thalami : Perinatal ischemia

A 6 yo male with delayed milestone. Preterm hospital delivery. Not cried immediately after birth, was in NICU for 3months. 

CT Brain salient features:

• Hyperdense thalami.
• Cortical atrophy.
• Ex vacuo dilatation of lateral ventricle with undulating walls suggestive of Gliosis and paucity of periventricular white matter - Periventricular leukomalacia.

Imaging findings and history supports Profund perinatal ischemia.

DDs of hyperdense thalami:
Krabbe.
GM Gangliosidosis.
Profund perinatal ischemia.

Hyperdense thalami : Krabbe disease

2yo male with delayed milestone. Birth history unremarkable.

CT brain salient features:

• Hyperdense thalami.
• Cortical atrophy marked in frontal regions.

Possible DDs: Krabbes disease > GM Gangliosidosis.

Profund perinatal ischemia unlikely as there is no supporting history and periventricular leukomalacia. 

Anaplastic Astrocytoma MRI

MRI Brain 

Sequences planned FLAIR, T2 , DWI, T2*GRE, T1W PC.

Single voxel MRS at short TE of 35ms.  

This MRI study of Brain shows:
An ill defined right insular focal parenchymal swelling, hyper intense on T2 and FLAIR with low signal on T1, a patchy enhancement on post contrast T1.
No dense dystrophic calcification or hemosiderin staining on T2*GRE.
Mild compression over right lateral ventricle.
No significant mass effect or mid line shift.
On MR Spectroscopy, markedly reduced NAA and Creatinine, raised choline.

Imaging findings are typical of Anplastic astrocytoma.


Anaplastic Astrocytoma

Syn: WHO Grade III astrocytoma - intermediate between low grade (diffuse) astrocytoma (WHO grade II) and GBM (grade IV),  Malignant astrocytoma, High grade astrocytoma.
Definition: A diffusely infiltrating astrocytoma, focal or diffuse anaplasia and marked proliferative potential.

AA contributes ~ 1/3 of all astrocytomas and ~ 25% of Gliomas.

Imaging wise diagnostic clues is an ill defined hemispheric white matter mass. May appear well circumscribed. Variable enhancement, typically none; may be focal or patchy. Commonly involve hemispheric WM, frontal and temporal lobes. In children, may involve Pons, thalamus and less commonly involves brain stern, spinal cord.

On CT, low density ill defined mass. Calcification and hemorrhage rare. Majority do not enhance. Enhancement may be focal, patchy and heterogeneous. If peripheral enhancement, consider malignant progression to GBM.
On MRI,
TlWI : Mixed isointense to hypointense WM mass. Areas of hemorrhage rare may appear bright on T1.
T2WI and FLAIR : Heterogeneously hyperintense, infiltrates adjacent brain. Involve and expand overlying cortex.
DWI: No diffusion restriction is typical.
T1 PC : Usually no enhancement. Less commonly focal patchy enhancement. Peripheral enhancement suggest GBM.
MRS: Elevated Cho/Cr ratio, decreased NAA

AA has histologic and imaging characteristics along spectrum between low grade astrocytoma and GBM.

Histopathological findings
Gross features are an infiltrating mass with poorly delineated margins, often expands invaded structures. May appear discrete but tumor always infiltrates adjacent brain.
Microscopic Features characterized by increased cellularity, marked mitotic activity, distinct nuclear atypia, High nuclear/cytoplasmic ratio, Nuclear/cytoplasmic pleomorphism, Coarse nuclear chromatin, No necrosis or microvascular proliferation. Immunohistochemistry: GFAP+ common, MIB-1: 5-10% (proliferation index)

Differential diagnosis
- Low grade glioma
Focal or diffuse white matter mass.
Typically non enhancing hemispheric mass
Indistinguishable without biopsy
- Glioblastoma multiforme (GBM)
Characterized by areas of necrosis and hemorrhages, enhancing rim.
Extensive surrounding T2/FLAIR signal
- Cerebritis
T2 hyper intensity and patchy enhancement
Diffusion restriction typical.
- Ischemia
Often wedge-shaped, involves GM & WM, area of involvement corresponds to vascular territory.
Restricted diffusion if acute/subacute stage of infarction.
Gyriform enhancement in sub acute ischemia.
- Oligodendroglioma
A focal cortical mass with variable enhancement.
Dense calcification common.
May be indistinguishable.

Clinical Presentation
Occurs at all ages, most common 40-50 years, M:F = 1.8:1
Signs and symptoms varies with location.
Seizures, focal neurologic deficit common. May have headache, drowsiness, vomiting.
Increased intracranial pressure.
Personality or behavioral changes.

Treatment
Resection and radiation therapy, +/- chemotherapy.


Reference: Anne G Osborn, Diagnostic imaging I-6.

Lower limb MR Angiography

Normal MR Venogram of brain

2D TOF non contrast MR Venogram

INTRACRANIAL VENOUS DRAINAGE

The venous drainage of the brain and meninges can be divided into the diploic veins, meningeal veins, dural sinuses, as well as the superficial and deep cerebral veins.

Dural venous sinuses are the major intracranial drainage channels lined by opposing layers of dura, are valveless and trabeculated. The major dural sinuses include the superior sagittal sinus, inferior sagittal sinus, straight sinus, occipital sinus, transverse sinuses, petrosal sinuses, sigmoid sinuses, sphenoparietal sinuses and cavernous sinuses. 

Superior sagittal sinus drains the superficial cerebral veins from the medial and lateral surfaces of the cerebral hemispheres, run antero posteriorly in the midline in a shallow groove along the inner table from the foramen cecum of the crista galli to the torcular Herophili. 

The torcular Herophili is the confluence of the superior sagittal sinus, the straight sinus, paired transverse sinuses and sometimes the occipital sinus. 

The inferior sagittal sinus travels antero posteriorly along the inferior free edge of the falx, joins great cerebral vein of Galen and ultimately drain into the straight sinus.

The straight sinus runs antero posteriorly in the mid line from the junction of the falx cerebri and the tentorium to the torcular Herophili. 

The occipital sinus is the smallest of the dural sinuses, may be present as accessory sinus, communicate torcular Herophili with the internal jugular. 

The paired transverse sinuses begin at the torcular Herophili and run antero laterally to become the sigmoid sinuses when turning inferiorly and medially at the posterior aspect of the petrous temporal bones. The transverse sinuses run in a groove along the inner table along the peripheral edge of the tentorium. In 25% of the cases, the transverse sinuses are unequal in size. An atretic segment in ~5%. In most of the cases the superior sagittal sinus drains preferentially into the right transverse sinus, while the straight sinus drains preferentially into the left transverse sinus.

The superior petrosal sinus extends from the posterior aspect of the cavernous sinus at the petrous apex to the sigmoid sinus along a dural attachment of the tentorium to the petrous temporal bone. It provides venous drainage from the pons, upper medulla, cerebellum, and middle ear.

The inferior petrosal sinus runs inferiorly along the petro-occipital fissure from the posterior aspect of the cavernous sinus (near the petrous apex). It traverses the pars nervosa compartment of the jugular foramen before emptying into the jugular bulb in the pars vascularis compartment. The paired inferior

petrosal sinuses are interconnected with the basilar venous plexus of the clivus and the intercavernous sinus (or circular sinus) to communicate with the cavernous, superior petrosal, marginal, and occipital sinuses.

The sphenoparietal sinus drains the superficial middle cerebral vein running along the greater sphenoid wing to the cavernous sinus. The sphenoparietal sinus often anastomoses with the basal vein of Rosenthal. The paired cavernous sinuses are irregularly paired venous spaces that lie on either side of the sphenoid bone in the central skull base region. They lie on either side of the sella turcica.

The internal cerebral veins are paired course posteriorly in the roof of the third ventricle between the leaves of the velum interpositum. The internal cerebral veins deviate from the midline at the pineal recess and proceed along the superolateral surface of the pineal body to converge at the level of the inferior splenium of the corpus callosum to form the great cerebral vein of Galen. Just before the convergence of the internal cerebral veins, the basal veins of Rosenthal join their ipsilateral internal cerebral veins.

Vein of Labbé is also known as Inferior anastomotic vein, connects the superficial middle cerebral vein of Sylvius from sylvinan fissure to the lateral sinus.

Vein of Trolard is also known as superior anastomotic vein connects the superficial middle cerebral vein of Sylvias from sylvian fissure to the superior sagittal sinus.

The dominance of these anastomotic veins is dictated by the relative size of the superficial middle cerebral vein and the other anastomotic vein. There is inverse relationship between the size of the superficial middle cerebral vein, the anastomotic vein of Trolard and the vein of Labbé, as all three share a same drainage area. 

Clinical significance : Isolated thrombosis of these vein is known, where MR Venogram may show controversial findings like normal or congenital absent ipsilateral lateral sinus with an adjacent hemorrhagic venous infarct which may be mistaken for hemorrhagic contusion. 

Source: 3D ANGIOGRAPHIC ATLAS OF NEUROVASCULAR ANATOMY AND PATHOLOGY, Neil M. Borden, MD.

Differentiation between ICA and ECA on MR Angio

On either side CCA divides into ICA and ECA at the level of upper border of thyroid cartilage.

Differentiating points between ICA and ECA on MR Angiogram

Caliber : ICA relatively larger in diameter than ECA.
Branches in neck: Look for the side branches, a branch arising from the vessel it has to be ECA as ICA gives no neck branches.
Alignment : ECA is in alignment with CCA where as ICA has a sharp angulation at its origin and then ascend upward, this is to reduce chances of ascend of emboli from CCA into ICA intra cranially.
Bulbar portion: a mild smooth dilatation involving proximal most portion of ICA near its origin is normal bulbar portion.
Location : on cross sectional row images ICA is anterio medial to ECA. 

Vascular territory of brain

To understand vascular supply of brain we can divide it into supratentorial and infratentorial parenchyma.

Supra tentorium composed of cerebral hemispheres on either side of mid line and deep grey nuclei at the core.

Cerebral hemispheres has frontal lobes anteriorly, occipital lobes posteriorly, parietal lobes cranially, temporal lobes caudally. The frontal lobe can be divided into medial or para sagittal portion and lateral portion, temporal lobes divided into medial and lateral portions. Occipital lobes divided into medial and lateral portions.

Deep grey nuclei at the core consist of bilateral Basal ganglia anteriorly, which in turn composed of caudate and lentiform nuclei and thalami posteriorly on either side of third ventricle. 

Infra tentorium composed of cerebellum and brain stem.

Cerebellar hemispheres divided into cranial and caudal portion. The caudal portion divided further into major posterior portion and smaller anterior portion.

Brain stem which is composed of mid brain, Pons and medulla.

ACA, MCA and PCA give cortical branches to cerebral hemispheres.

Para sagittal frontal lobe and cingulate gyri - cortical  ACA territory.

Medial occipital and medial temporal lobes - cortical PCA territory.

The remaining major lateral portions of cerebral hemispheres, the perisylvian cerebral cortex – cortical MCA territory, some further divide it into superior division territory which is the portion anterior and cranial to sylvian fissure and inferior division territory which is the portion caudal and posterior to sylvain fissure.

ACA, MCA and PCAs, their proximal most portions gives perforator branches to the deep grey nuclei at the core.

ACA a1 segment gives medial lenticulostriate perforators and MCA m1 segment gives lateral lenticulo striate which supply basal ganglia. PCA p1 segment gives thalamostriate perforators which supply thalami and mesencephalic mid brain.

Pica, intra cranial branch from each vertebral supply major posterior part of caudal portion of cerebellum on either side and medulla.
Vertebral join to form Basilar.

Aica, from proximal portion of basilar supply the remaining small anterior part of caudal portion of cerebellum on either side.

Superior cerebellars, from distal most portion of basilar supply the cranial portion of cerebellar hemispheres on either side.

Basillar gives Pontine perforators on either side supply Pons.

Between cortical branches of ACA, MCA and PCA we have cortical border zone. Anterior cortical border zone between ACA-MCA and posterior cortical border zone between MCA and PCA.

Between cortical branches and deep branches (perforators) we have deep (internal) border zone. 

Normal MR Angio Brain and Neck

2D TOF Non contrast MR Angiogram of Neck

Arch of aorta gives three major branches.

1^st Innominate, a small common trunk which divides further into right subclavian and right CCA.

2^nd Left CCA.

3^rd Left Subclavian.
(CCA on right side is branch of innominate and on left side arises directly from arch of aorta)

CCA on either side ascend upward and divides at the level of thyroid into ICA and ECA.

ICA ascends intra cranially and represents afferent of anterior circulation on either side.

Subclavian on either side gives off vertebral which ascend upward intracranially and represent afferent of posterior circulation.

3D TOF Non contrast MR Angiogram of Brain

Intra cranially on either side, ICA which represents anterior circulation divides into ACA and MCA. Vertebrals which represents posterior circulation join to form basilar in front of Pons, which divides further infront of mid brain into to PCAs for each side.

ACAs from each side extend antero medially and ascend along interhemispheric fissure.  The anterior communicating artery (Acom) forms a bridge between the two ACAs and contribute in completion of circle of Willis anteriorly.

ACAs on either side, its proximal most portion, proximal to Acom is pre communicating (a1) segment, distal portion is post communicating (a2) segment and divide further into cortical branches (a3).

MCAs on either side, its proximal portion, the main stem (m1) extend laterally along Sylvain fissure and divides into superior and inferior divisions (m2) , ascent over cerebral convexity in perisylvian region and divide further into cortical branches (m3).

PCA on either side extend posteriorly. The posterior communicating artery (Pcom) , a small branch from supra clinoid portion of ICA extend posteriorly between ICA and PCA and contribute in completion of circle of Willis by forming a bridge posteriorly laterally on either side.

PCAs on either side, its proximal most portion, proximal to Pcom is pre communicating (p1) segment, distal portion is post communicating (p2) segment and divide further into cortical branches (p3).

Hyperdense dural venous sinuses on CT

A 30 yo female with 2weeks history of headache.

CT study of brain show hyperdensity in the region of right transverse sigmoid sinus – a subtle finding. No other parenchymal abnormality. It’s better to advise MR in such case or if available you yourself run needed MRI Brain sequences and Venogram to rule out CVT. At the most u may need an axial FLAIR and a noncontrast 2D TOF MR Venogram.

In this case there is loss of normal T2 flow void in the region of right transverse sigmoid sinus and superior sagittal sinus with an isointense soft tissue signal intensity material occupying the sinus. Right transverse sigmoid sinus not visualised on MR Venogram with poor flow related signals in the region of major portion of superior sagittal sinus implies to thrombosis.

Sometimes despite of very obvious hyper density in the region of dural venous sinuses, surprisingly, the MR Brain and Venogam may turn out normal. The possible explanation for this are either 1. Increased blood density due to dehydration, physiological polycythemia  or 2. Dominant sinus due to hypoplastic contralateral lateral sinus.

Spinal epidural Pseudotumour MRI

Spinal Epidural Inflammatory Pseudotumor : A rare case report of histo pathologically proven spinal epidural inflammatory pseudotumor in dorsal region.

A 50 yo male with presented with urinary incontinence and progressive bilateral lower limb weakness. n associated dull pain for last 4 months localized in mid dorsal region along mid line.
Hb, white blood cell count, ESR, C-reactive protein level, Liver function test normal.
Xray chest normal.

MRI Dorsal spine (Sagittal,Axial T2 and T1w images, Post contrast Sagittal Fat Sat T1w images)

Sagittal T2 and T1w

Axial T2 and T1w

PC Sagittal Fat sat T1w

This MRI study shows:A focal posterior epidural lentiform shaped soft tissue signal intensity with homogenous enhancement on post contrast T1w images.
Mild focal cord compression.
The soft tissue is encasing exiting nerve roots at this level on either side.
An associated para spinal soft tissue on left side.

Imaging wise possible DDs given were: Lymphoma, Metastasis, Pseudotumur.

Posterior decompressive laminectomy performed. Histopathology revealed diagnosis of Inflammatory pseudotumour.

INFLAMMATORY PSEUDOTUMOR 

Syn : Inflammatory myofibroblastic tumor.
A benign tumor like lesion of unknown cause, which has been described in very small numbers at various locations throughout the body.
It is believed that inflammatory pseudotumor is an inflammatory process that includes a diverse group of lesions characterized by inflammatory cell infiltration and variable fibrotic responses.
IP is a chronic inflammatory tumefaction of unknown origin characterized by proliferation of myofibroblastic spindle cells with mixed inflammatory infiltrates of plasma cells, lymphocytes, Eosinophils, and histiocytes.
IP is found in the lung and occasionally in the mouth, gastrointestinal tract, thyroid gland, kidney, lymph nodes, and skin.
The pathogenesis of IP remains a matter of debate. Some cases have been associated with malignancy or tuberculosis as satellite lesions. The multiplicity of sites that can be involved suggests no particular route of entry or any specific agents. Prior surgery, trauma, or immune disturbances, in addition to infection are included for the possible etiology.

IP has no distinguishing characteristics, either clinically or radiologically. Hence, the diagnosis of inflammatory pseudotumor can be made only after other specific disorders are ruled out.

MRI with contrast is considered as investigation of choice. Signals on MRI varies, hypointense to iso intense on T1 and hyper intense to hypo intense on T2w images. Enhancement pattern is often intense and homogenous. Despite the limited number of cases, low signal intensity on T1 and T2-weighted images with homogenous strong enhancement on post contrast are considered as characteristic findings of Pseudotumor on MRI.
Low signal intensity on T2 weighted images explained by a relative lack of both free water and mobile protons within fibrotic lesions of this fibrosing inflammatory pseudotumor.
Common differential diagnosis on MRI includes spinal lymphoma, metastatic tumor, multiple myeloma,and meningioma. Without a biopsy, differentiating
the lesion is very difficult.

IP has been treated with surgical removal and steroid therapy with good results.

Reference : Inflammatory Pseudotumor in the Epidural Space of the Thoracic Spine: A Case Report and Literature Review of MR Imaging Findings; Ho Jun Seol, Sam Soo Kim, Ji Eun Kim; AJNR Am J Neuroradiol 26:2667–2670, November/December 2005.