Ossification of Posterior Longitudinal Ligament (OPLL)

 

Above lateral cervical radiograph and the T2, T1 weighted MR images show thickening and ossification of the Posterior Longitudinal Ligament (OPLL) posterior to C2 and C3 vertebral bodies. The PLL ossification would be seen as hypointense signal intense thickening of the PLL in both T1 and T2 images. Narrowing of the spinal canal with compression of the thecal sac and the cord is present at C2/C3 levels.

Dilated occipital emissary vein in Idiopathic Intracranial Hypertension

 25Y female who presented with complaints of chronic headache, on examination was found to have bilateral papilledema. An MRI with MR venogram was taken to look for features of Idiopathic Intracranial Hypertension. MRI findings were partial empty sella, with minimal increase in the retrobulbar optic nerve sheath CSF content (not shown). No vertical tortuosity of the optic nerves were seen in the MRI.  

MR Venogram showed mild distal transverse venous stenosis. A dilated occipital emissary vein was noted with diameter of the intraosseous component measuring 4.5 mm and the diameter of the proximal extracranial segment measuring 4.7 mm. Rest of the major intracranial venous sinuses appear normal.

Emissary veins of the skull base and posterior fossa direct the cerebral blood flow into the cervical outflow tracts. These include the condylar (anterior, posterior and lateral) emissary veins, mastoid emissary vein and the occipital emissary vein. The occipital emissary vein is seen near the midline of the squamous occipital bone and it connects the torcula or the distal superior sagittal sinus to suboccipital veins, which further drain into the vertebral venous plexus and / or the deep cervical vein. 

Enlarged occipital emissary veins have been described in craniosynostosis , increased ICT and in thrombosis of transverse sinus or sigmoid sinus. 

Idiopathic Intracranial Hypertension (Syn: Benign intracranial hypertension or pseudotumor cerebri syndrome (PTCS)) are characterized by findings of enlarged empty sella, papilledema, vertical tortuosity of optic nerves, dilated subarachnoid spaces around cranial nerves and dural venous sinus stenosis (usually bilateral distal transverse sinuses). The occipital emissary vein in patients with idiopathic intracranial hypertension may be dilated because it acts as a collateral venous channel and its dilatation is considered a possible marker for IIH.

Reference: Hedjoudje A, Piveteau A, Gonzalez-Campo C, Moghekar A, Gailloud P, San Millán D. The Occipital Emissary Vein: A Possible Marker for Pseudotumor Cerebri. AJNR Am J Neuroradiol. 2019 Jun;40(6):973-978. doi: 10.3174/ajnr.A6061. 

Isolated Area Postrema Syndrome (APS) presenting as intractable nausea and vomiting (NMOSD)

 Area Postrema (AP) is an emetic reflex center, one of the circum-ventricular organs that is outside the blood-brain barrier(BBB). It is located in the dorsal aspect of the medulla, at the caudal end of the fourth ventricle. AP along with Nucleus Tractus Solitarius (NTS) and dorsal motor nucleus of Vagus forms the dorsal vagal complex, where most of the vagal afferents terminate. AP by its location outside the BBB is exposed to the toxins in the blood. Activation of the AP brings nausea and vomiting, due to its projections into the NTS. 

AP through its hypothalamic,brainstem connections also regulate fluid balance, immunomodulation etc. It also chemo-sensitive neurons regulating hiccups. 

Neuro Myelitis Optic Spectrum of Disorders (NMOSD) are a group of autoimmune inflammatory demyelinating diseases of the CNS. Most of these show characteristic antibody to aquaporin-4 (AQP-4) water channel. 

 Attacks of intractable nausea, vomiting or hiccups (INVH) in the presence of a dorsal medullary lesion is called as the Area Postrema Syndrome (APS) and upto 30% of NMOSD patients will have APS during their disease course. 

NMOSD lesions in the Area Postrema shows loss of AQP-4 immunoreactivity and inflammation and characteristically lacks necrosis and demyelination which is seen in spinal cord and optic lesions, explaining reversibility of the symptoms. Patients have to tested for Serum and CSF AQP4-IgG antibodies. 

Isolated APS is easily mistaken clinically and is often attributed initially to other causes like gastritis including H.Pylori, GERD, Cholecystitis, Pancreatitis, food poisoning, gastroparesis etc. 

Immunotherapy usually results in rapid relief of symptoms usually within 2-3 days, responding to Methyl Prednisolone or Immunotherapy in most cases. Refractory cases may need drugs like Azathioprine, MMF, Rituximab.   

Below are the MRI images of a young female with intractable nausea and vomiting. 

T2 and T2 FLAIR hyperintensity noted in the region of the Area Postrema, called the Inverted-V sign.

Bilateral symmetrical normal optic nerves.

No restricted diffusion seen in the abnormal signal areas of Area Postrema.

Corresponding sagittal T2 FLAIR image showing the level of Area Postrema.
Abnormal signal intensity is also seen in the inferior colliculi of midbrain in the sagittal image. 

Diagram showing the location of AP, NTS in the dorsal medulla.

Persistent Trigeminal Artery (PTA), Tau sign

Persistent Primitive Trigeminal Artery is one of the persistent carotid-vertebro-basilar anastomoses. PTA arises from petrous-cavernous junction, runs posterolaterally along the trigeminal nerve, crosses over or through dorsum sella.  

Two types of PTA have been described. 

Saltzman Type I : PTA supplies the distal basilar artery. PComs are usually absent. The distal basilar artery is absent or hypoplastic. Distal vertebral arteries are also hypoplastic. 

Saltzman Type II : PTA supplies the Superior Cerebellar Arteries, with PCAs supplied by the PCom. 

TOF MRA images showed Saltzman type I PPTA, where the PTA is seen replacing the distal basilar artery. 

Sagittal MIP MRA image showing the distal basilar artery completely supplied by the PTA. 

The Tau sign, resembling a 'T' is classically described in the sagittal images. 

Perineural cysts (Tarlov cysts) of the cervical spine

Plain CT Brain findings in an adolescent patient with Tuberous Sclerosis

Tuberous Sclerosis (TS) or Bournville disease is a rare Autosomal Dominant (AD) neurocutaneous syndrome (phakomatoses) characterized by development of multiple benign tumors of in various organs. Since the characteristic clinical triad mentioned is mental retardation, adenoma sebaceum and seizures is uncommon, imaging plays an important role in diagnosis of this condition.Sometimes intrauterine diagnosis of TS of the fetus can be suspected with visualization of cardiac rhabdomyomas in ultrasound.

Below are some of the features of TS detectable in plain CT, in a 16yr old patient.

Above image shows the presence of characteristic calcified and non-calcified sub-ependymal nodules (red arrows). Calcification of these subpendymal hamartomas is less frequent in early childhood, where as cortical/subcortical tubers can calcify as early as 2yrs of age.

Image showing multiple cortical and subcortical hypodensities suggestive of cortical tubers (blue arrows). Most of the tubers in TS are located in frontal lobe.

Left foramen of Monro region shows a relatively homogenous, non-calcified lesion (blue arrows) measuring AP dimension of ~13mm - suspicious of a Subpendymal Giant Cell Astrocytoma (SGCA / SEGA). These are considered WHO-Grade 1 tumors, eventhough there is a potential of causing obstructive hydrocephalus. These are theorized to evolve from the subpendymal nodules. Histologically both SGCA and subpendymal hamartomas show same appearance.SGCAs can show intense enhancement, and may show calcifications and heterogeneity.

Same lesion in sagittal reformat (golden arrow).

A few calcified cerebellar tubers (green arrows).

Above bone window images show multiple calvarial
small sclerotic areas of hyperostosis (orange arrows).

Parieto-occipital encephalomalacia in a child

 12yr old with repeated seizures.

Bilateral parietal and occipital gliotic-encephalomalacic changes are noted, almost in a symmetrical manner.

Cavernous Sinus Dermoid Cyst

Clinical History : 60yr old female patient with right 3rd nerve palsy. Suspecting a PCom aneurysm, CT angiogram was performed which showed no intracranial aneurysms.

However a heterogenously hypodense non-enhancing lesion was seen in the right cavernous sinus, with cavernous ICA seen medially displaced. Lesion anteriorly showed markedly hypodense area of negative attenuation varying from -100 to -150HU, suggesting intralesional fat. Posterior rim of the lesion showed small calcfications. Lateral hyperdense rim was thought to represent the thickened dural layer of cavernous sinus.

Nasu Hakola disease

• Rare hereditary Autosomal Recessive disorder.
• Also known as Polycystic Lipomembranous Osteopathy with Sclerosing Leukoencephalopathy (PLOSL). 
• Progressive presenile dementia, with associated recurrent bone fractures, due to cystic lesion of long bones. 
• Progresses in  4 stages: Latent, Osseous, Early neurologic and late neurologic. The disease may not be recognized until the neurologic symptoms start in the third or fourth decade, characterized mainly by frontal lobe symptoms of loss of concentration, loss of social inhibition, loss of judgement etc.
• Radiologically white matter hyperintensities of brain, neuroparenchymal atrophy, basal ganglia calcifications, especially putaminal etc are noted. Caudate head atrophy with widening of frontal horns as in Huntingtons disease may be seen, with increased intercaudate distance to inner table width ratio.
• No treatment is available at present and death usually occurs by 5th decade.

Acute PCA territory infarct

Right occipital lobe and thalamic involvement.

Right posteromedial temporal lobe infarct.

Absent flow in right PCA (P2) (Black arrow) in TOF MRA MIP images. White arrow pointing to left PCA P2 segment.

The major PCA segments are the Pre-communicating / Peduncular / P1 segment, Ambient / P2 segment and the Quadrigeminal / P3 segment.

The major branches from P1 segment include Posterior thalamo-perforating arteries and the median posterior choroidal artery.

Major branches from P2 segment of PCA includes lateral posterior choroidal artery and posterior choroidal artery.

Inferior temporal arteries, parieto-occipital artery, calcarine artery, posterior pericallosal (splenial) arteries are the major branches of the P3 or quadrigeminal segment of PCA.



Reference : Diagnostic Neuroradiology, Anne.G.Osborn, 1994.

What's your diagnosis? : Case 3 [June 25th, 2017]

Post your answers as comment below. Answer and brief discussion will be posted in few days.

Acute intracranial hemorrhage with blood-fluid level

Blood-fluid level or hematocrit level or 'Sedimentation level' in spontaneous parenchymal hemorrhage could be due to coagulopathy or when the patient is on anti-coagulation medications. It can also be seen less often in cases of AVM or tumoral bleed (both primary and metastatic), Amyloid Angiopathy and sometimes in Radiation Induced Necrosis.


Approximately 60% of patients with increased PT/APTT can have blood-fluid levels in intracranial hemorrhages as per the reference below. 'Fluid-blood levels in acute intracerebral hemorrhage are moderately sensitive to the presence of coagulopathy (ie, abnormal prothrombin time and partial thromboplastin time) and highly specific for this condition. Thus, an intracerebral hemorrhage with a fluid-blood level should prompt a thorough search for coagulopathy because early treatment of this condition may improve the 40% mortality in these patients'.

AJNR Am J Neuroradiol. 1994 Feb;15(2):217-23.
Sensitivity and specificity of fluid-blood levels for coagulopathy in acute intracerebral hematomas.

Developmental Venous Anomaly with Cavernoma

Lateral Medullary Syndrome MRI

What's 'GRE Susceptibility Vessel Sign' ?

(Above image showing the Susceptibility Vessel Sign : hypointense signal on SWI of right vertebral artery (V4 segment), more or less equivalent to hyperdense Vertebral Artery on CT).

Thrombi are mainly of three types based on their composition : platelet rich (white) thrombi, red thrombi containing rich fibrin network and RBCs and finally the mixed ones. White thrombi are formed mainly in atherosclerotic plaque ruptures, where as red thrombi are formed in low pressure systems like cardiac or venous systems.

The oxyhemoglobin which gets degraded into de-oxy hemoglobin, methemoglobin and hemosiderin, all have paramagnetic properties and produces susceptibility artifacts in GRE images. This concept is the main core of Susceptibility Vessel Sign.

Teaching Point : GRE SVS is associated with red thrombi and thereby favors a Cardio-Embolic Stroke in most cases. And it also signifies increased chance of subsequent spontaneous recanalization and also increased success rates with fibrinolytic therapy. 

 

Exceptions :

1.SVS –ve cardio-embolic thrombi : 

Can occur if MRI was taken before the degradation of Oxy-Hb to Deoxy-Hb (which usually occurs in few hours) OR due missing the section of small thrombus in GRE due to the interslice gap.

2.SVS +ve (Large Artery) Atherosclerotic thrombi :

due to the formation of white thrombus initially, can lead to stagnant or reduced flow velocity within the vessel, there by gradually causing increased fibrin and RBC content of thrombus.


References :
1. Significance of Susceptibility Vessel Sign on T2*-Weighted Gradient Echo Imaging for Identification of Stroke Subtypes. Kyung-Hee Cho, MD; Jong S. Kim, MD, PhD; Sun U. Kwon, MD, PhD; A-Hyun Cho, MD; Dong-Wha Kang, MD, PhD. Stroke, November 2005.

Intracranial Arachnoid Cyst : Galassi Type I

By definition an ARACHNOID CYST is an intra-arachnoid CSF-filled sac that does not communicate with the ventricular system. Best diagnostic clue is a sharply demarcated, round/ovoid extra-axial cyst that follows CSF density/signal and shows no diffusion restriction or enhancement.

As its an extra-axial lesion it does buckles the grey-white interface and may also remodel / cause scalloping / thin adjacent bone.

It comprises of ~1% of all intracanial masses. Majority (~60%) are located in the middle cranial fossa, anterior the the temporal lobe, with posterior displacement of MCA. Less common sites of arachnoid cysts include CP angle, Suprasellar region, convexity and quadrigeminal cistern.

The major differential diagnosis will be an epidermoid cyst, porencephalic cyst, neurenteric cyst and neuroglial cysts. DWI and T2 FLAIR sequences are the most helpful in arriving at a diagnosis.

Epidermoid cysts show diffusion restriction. These lesions are only partially suppressed in T2 FLAIR images and looks 'dirty'. These are plastic lesions, which instead of displacing vessels engulf them and insinuate into the sulcal spaces.

A porencephalic cyst will usually have history of previous trauma or infarct. And these are usually surrounded by gliotic areas, not displaced cortex.

Neuroglial cysts are usually intra-axial.

Neurenteric cysts are usually seen in posterior fossa and they often contain proteinaceous fluid.


The following images depict the typical imaging findings of a middle cranial fossa arachnoid cyst.

In the anterior temporal location, it may be associated with temporal lobe hypoplasia. Above image shows complete homogenous supression of the signal of the arachnoid cyst in T2 FLAIR images.

 Above image shows the lesion being isointense to CSF in T1 WI.

In DWI-ADC, contrast from an epidermoid cyst, the arachnoid cyst shows no diffusion restriction.

Galassi et al. had classified middle cranial fossa arachnoid cysts into 3 types long back in 1982, this classification is still being followed.

Type I cyst : Located in the Sylvian fissure, in the anterior temporal region, posterior to the sphenoid ridge, without any mass effect. These freely communicate with the subarachnoid space in Contrast CT cisternogram or in Phase Contrast MR evaluation.

Type II cyst : Located in the mid and proximal portions of Sylvian fissure, larger and rectangular in configuration. They communicate with subarachnoid space but slowly.

Type III cyst : Usually do not communicate with subarachnoid cyst, largest, lentiform in shape, will result in signficant mass effect and midline shift.


NOTE : A very large arachnoid cyst can show T2 slightly hypointense signal due to internal flow.

Diagnosis Please : 15.07.2016

Middle aged male presented with repeated falls, altered behavior. No seizures.

 

Diagnosis Please : 14.07.2016

 Clinical History : Middle aged female with chronic headache and recurrent visual blurring. 

What's your diagnosis based on these MR images?

ANSWER

 

Prominent Lateral Tentorial Venous Sinuses

TENTORIAL SINUSES

Numerous tentorial sinuses drain near the confluence / torcula herophili. These venous channels may provide significant drainage for adjacent cerebellum. They can be enlarged significantly if the straight sinus or superior sagittal sinus is occluded.

Meningioma / hemangiopericytoma presenting as proptosis

This 60yr old male patient presented with gradual, but progressively increasing proptosis, over the past 10 years. There was no history of diplopia. He had developed pain in right orbit, for which he took medical help.