At this point, what is your diagnosis? Meningioma…… right?

Our pre-operative diagnosis was also meningioma. Only concern was that the diffusion restriction was little too much for a meningioma, even for a densely cellular anaplastic meningioma.

There were two surprises for us both from surgeons as well as from pathologists. When the surgeons opened the dura, the mass was intra-axial! When the pathologists saw the tumor under microscope, they found diffuse large B-cell lymphoma with very high proliferative index (90-95%) and officially they called it “Large B-cell lymphoma, diffuse, with high proliferative rate and intermediate features between Burkitt lymphoma and large cell lymphoma (WHO classification 2008)”.

This is a very interesting case because the tumor grew without following the ‘basic rules of neuroradiology’. Though the tumor arose from intra-axial compartment the way it enlarged and its internal morphology gave it a look of an extra-axial mass. This is not an uncommon dilemma of day to day neuroradiology practice. The best way to differentiate between pathologies at a given anatomic location is to execute a mental workout (I call it ‘Curé’s algorithm’) which is consisting of a) correct identification of the compartment from where the lesion arises, b) recall of normal structures of that compartment, c) recall of possible pathologies that can arise from the normal structures of that compartment, d) careful evaluation of the imaging appearances of the lesions in different imaging sequences/modalities and finally e) to perform an intensive mental database search for ‘curve fitting’ of the imaging appearances with the possible pathologies considered before. As the first step of the ‘Curé’s algorithm’ went wrong in this case, we ended up a wrong diagnosis even though there were subtle clues to the right diagnosis.

Though the patient presented with relatively short duration of frontal lobe symptoms and the tumor had prominent diffusion restriction we did not consider primary CNS lymphoma (PCNSL) as our provisional diagnosis because a) we thought the tumor was extra-axial, b) the incidence of primary leptomeningeal lymphoma (LL) is exceedingly rare and typical LL does not look like this, c) the tumor had high rCBV, a perfusion characteristic perfusion characteristic typically not seen in lymphoma and finally d) all imaging appearances other than diffusion restriction was ‘best-fit’ for meningioma.

PCNSL is an extranodal manifestation of non-Hodgkin’s lymphoma limited in central neuraxis including orbit, leptomeninges, spinal cord and cranial/spinal nerves without any other systemic manifestation. PCNSL constitutes 6-15.4% of all brain tumor, more common in men and usually occurs in patients >60 years of age. PCNSL is more commonly supratentorial (87%) and solitary (66%) in immunocompetent patient. Primary leptomeningeal lymphoma is a rare subtype of PCNSL limited to the meninges. Primary ocular lymphoma is another rare subset of PCNSL that involves vitreous, sub-retinal space or anterior chamber without systemic or CNS involvement. Up to 90% of these patients subsequently develop CNS lymphoma. Some authors also consider neurolymphomatosis as a variant of PCNSL. Neurolymphomatosis is very difficult to diagnose on MRI, particularly if the patient has no known lymphoma, either systemic or PCNSL.

The imaging appearance of the tumor depends upon the immune status of the patient. In immune competent patients, PCNSL is solid, T1 hypointense and iso- to slightly hyperintense on T2 weighted sequence. It can involve any area of brain but frontal lobe and basal ganglia are most commonly involved. It enhances brightly and homogenously with contrast. On diffusion weighted imaging, there is prominent diffusion restriction due to intense ‘packing’ of the tumor. Lymphoma is usually cold on perfusion imaging. PCNSLs in immunocompromised patients typically appear as peripherally located ring-enhancing lesions with central necrosis. They are often multiple. There may be diffusion restriction only at the periphery.

Iwamoto FM, DeAngelis LM. An update on primary central nervous system lymphoma. Hematol Oncol Clin North Am. 2006;20:1267-85

Shenkier TN. Unusual variants of primary central nervous system lymphoma. Hematol Oncol Clin North Am. 2005;19:651-64

On surgery, the mass was encapsulated but the capsule was tightly adherent to the cerebellum. On histopathology, the tumor turned out to be a malignant fibrous histiocytoma (MFH) with 40% MIB-1 index.

MFH, the most common soft tissue sarcoma in adults, arises from fibroblasts, myofibroblasts or undifferentiated mesenchymal cells. Most patients are between 50 and 70 years old. Men are affected 2-3 times more commonly than women. Most MFHs arise de novo however, they can occur secondary to prior radiation, trauma, Paget’s disease, chronic osteomyelitis or benign bone tumors. MFH most commonly occurs in lower extremity. Head and neck area is involved up to 10% of cases.  In head neck, nasal cavity and paranasal sinuses are most commonly involved. It has variable appearances on CT and MRI. On CT, this is usually large lobulated sift tissue mass which is isodense to muscles with destruction/remodeling of adjacent bone. There may calcification in up to 5-20% of patients. On MRI, they are isointense to muscle on T1 weighted sequence and heterogeneously hyperintense on T2 weighted sequence. This tumor can have both solid and cystic component. Solid portion enhances intensely. Spontaneous hemorrhage is frequently seen and can obscure the primary tumor. The diagnosis is important because it is a malignant tumor and post-resection radiation therapy is required for better tumor control. MFH also has poor prognosis.

Suggested readings:

Nakayama K, Nemoto Y, Inoue Y, Mochizuki T, Soares SB, Ohata K, Katsuyama J, Onoyama Y and Wakasa K. Malignant fibrous histiocytoma of the temporal bone with endocranial extension.AJNR Am. J. Neuroradiol. 1997; 18: 331 – 4.

Park SW., Kim HJ., Lee JH, and Ko. YH. Malignant Fibrous Histiocytoma of the Head and Neck: CT and MR Imaging Findings. AJNR Am. J. Neuroradiol. 2009; 30: 71 – 6.

Physical examination showed no chemosis, vision loss or cranial nerve palsies.  Because of this the patient was brought back for repeat contrast enhanced CT of the orbits with Valsalva maneuver.  This study showed mild additional enlargement of the already prominent left superior ophthalmic vein and also of the right sided one (see below).  The combination of imaging and clinical findings was thought to be most compatible with orbital varices.  The patient opted for conservative management.

Orbital varices are hamartomas composed of slow flow, low pressure and thinned walled and distensible blood vessels.  As they communicate with the rest of the circulation, they enlarge with Valsava, bending or prone position, and coughing and straining.  They produce proptosis which may be painful and because they may bleed, their symptoms may become acutely exacerbated.  They may also erode adjacent bone.  Treatment is very difficult and is reserved for those with repeated hemorrhages, thrombosis, optic nerve compression and disfigurement.  Orbital vascular processes included in the differential diagnosis are carotid cavernous fistulas of both types and less likely, venous thrombosis.

In CC fistulas, the ipsilateral cavernous sinus may be enlarged particularly in the direct ones (see below).  Extra-ocular muscles may also be large and the retro-ocular fat may have a “dirty” appearance.  In most patients with direct CCFs, chemosis, decreased vision and cranial nerve palsies are present.  Acute thrombosis of the superior ophthalmic vein may present with symptoms that are similar to those of a direct CCF.  Indirect CCFs may have less acute symptoms and be clinically similar to varices.  The diagnosis is confirmed with catheter angiography as shown here.

Suggested readings:

YO Arat, ME Mawad, M Boniuk. Orbital Venous Malformations: Current Multidisciplinary Treatment Approach. Arch Ophthalmol 2004; 122: 1151 – 1158

N Islam, K Mireskandari, GE Rose. Orbital varices and orbital wall defects. Br J Ophthalmol 2004; 88: 1092 – 1093

A Weill, C Cognard, L Castaings, G Robert, J Moret. Embolization of an orbital varix after surgical exposure. AJNR Am. J. Neuroradiol. 1998; 19: 921 – 923

Further questioning of patient disclosed that the symptoms had had a sudden onset 7 days earlier.  The diagnosis of subacute infarction of the right posterior inferior cerebellar artery territory was considered as the most likely cause of the findings.  The patient was followed and repeat MRI three months later demonstrated only malacia and atrophy in the location.

Llermitte-Duclos disease (a.k.a. dysplastic gangliocytoma of the cerebellum) is the CNS hallmark of Cowden syndrome.  It is probably a malformative hamartoma of the cerebellum seen nearly exclusively in this syndrome.  The typical lesion has a “corduroy” or “tiger striped” appearance, does not enhance after contrast, has restricted diffusion (presumably due to its high cellularity), and normal-to-increased perfusion. MRS shows low NAA, decreased Cho/Cr, elevated lactate and high myoinositol and at times the spectra may be near normal (see below).  PET shows increased FDG accumulation.  Thus to differentiate it from an infarct with similar appearance perfusion and PET studies are best when in doubt.  Additionally, contrast enhancement in Llermitte-Duclos is extremely rare.

Suggested readings:

Klish J, JUengling F, Spreer J, Koch D, et la. Llhermitte-Duclos disease: assessment with MR imaging, positron emission tomography, single photon emission CT, and MR spectroscopy. AJNR Am J Neuroradiol 2001; 22: 824-30

Moonis G, Ibrahim M, Melhem ER. Diffusion-weighted MRI in Llermitte-Duclos disease: report of two cases. Neuroradiology 2004; 46: 351-54

Awwad EE, Levy E, Martin DW, Merenda GO. Atypical MR appearance of Lhermitte-Duclos disease with contrast enhancement. AJNR Am J Neuroradiol 1995; 16: 1719-20

Before surgery, a chest radiograph was obtained and showed bilateral hilar nodularities.  Surgery was postponed and a chest CT confirmed the hilar abnormalities and showed parenchymal abnormalities (see below).  Based on the findings a work up for sarcoidosis was performed and was positive.  The patient received steroids and her vision improved.  Follow-up brain MRI showed the lesion to be smaller.

Sarcoidosis is more common in younger (average age: 35 years) African American women.  Over one half of patients will have neurological complaints, generally longstanding.  In about 10% of patients, sarcoidosis is isolated to the CNS.  The most common symptoms are headaches and cranial nerve palsies (mostly affecting the V, VII, VIII and III).  Approximately 15% of patients have dural disease (which is often accompanied by leptomeningeal involvement).  Dural disease responds well to treatment.  Conversely, intra-axial disease leads to seizures and is more difficult to control.  Angiotensin converting enzyme test is positive in 50% of patients.  The MRI findings on our case are typical of sarcoidosis.  The very low T2 signal can be seen in up 20% of meningiomas (particularly of the fibroblastic or transitional types).  Remember that most meningiomas are isointense to gray matter on T2WI (see below).

Suggested readings:

Chirstoforidis GA, Spickler EM, Recio MV, Mehta BM. MR of CNS sarcoidosis: correlation of imaging features to clinical symptoms and response to treatment. AJNR Am J Neuroradio 1999; 20: 655-669

Shag R. Roberson GH, Cure JK. Correlation of MR imaging findings and clinical manifestations in neurosarcoidosis. AJNR AM J Neurodiol 2009; 30: 953-961

Smith JK, Matheus MG, Castillo M. Imaging manifestations of neurosarcoidosis. AJR 2004; 182: 289-295

Analysis of axial images showed that the mass involved the spinal canal but extended out into the paraspinal regions, including the right psoas muscle, via several neural foramina.  The diagnosis was reconsidered to include giant invasive spinal schwannoma (histologically confirmed later).

Schwannomas are the most common primary spinal tumor occurring predominantly in the cervical and thoracic regions.  Tumors of the cauda equina region represent only 6% of all spinal masses; most are schwannomas. “Giant” schwannomas are rare, long lesions that expand, remodel or destroy adjacent bones.  When they extend to extra-spinal myofascial planes, they are considered “invasive”.  Symptoms vary from severe to mild. Total excision is advocated but not always feasible.  Spinal fusion after tumor resection is needed in most patients.  Perhaps, fewer than 20 cases of giant schwannomas are found in the modern literature nearly all of them in the lumbosacral region. They are not associated with NF-2. The main differential diagnosis is that of myxopapillary ependymoma. Giant ependymomas are more common in younger individuals and despite attaining large size they do not tend to produce the focal bone scalloping and paraspinal involvement that giant schwannomas typically show (see illustration below). Mutiple schwannomas, as seen in NF-2 could also have a similar appearance.

References:

Sridhar K, Ramamurthi R, Vasudevan MC, Ramamurthi B. Giant invasive spinal schwannomas: definiation and surgical management. J Neurosurg (Spine) 2001; 94: 210-215

Hung CH, Tsai TH, Lin CL et al. Giant invasive schwannoma of the cauda equina with minimal neurologic deficit: a case report and literature review. Kaohsiung J Med Sci 2008; 24: 212-217

Guyotat J, Fishcer G, Remond J et al. Giant ependymoma of the cauda equine. Long-term development apropos of 7 cases. Neurochirurgie 1993; 39: 85-91

Analysis of images showed an artifact involving the right lower side of the skull seen only on the DWI, ADC and a T2* sequence.  This magnetic susceptibility artifact was found out to have been due to a metal chain.  Upon arrival in our CT scanner, the technologists removed the chain to prevent artifacts.

Discussion:

In FLAIR images, an inversion pulse is applied to suppress the normal signal intensity from CSF.  Multiple causes result in T2 prolongation of CSF signal making it bright on FLAIR and include: inhaled oxygen, increased proteins due to presence of blood or infection, tumor, propofol, and hyperdynamic pulsations such as those seen in the basilar cisterns particularly around arteries.  Artifacts resulting in hyperintense CSF include: motion, inhomogeneity in amplitude of initial inversion pulse, chemical shift, cross-talk, truncation, suboptimal inversion time, overlapping of imaging planes and as in this patient, magnetic susceptibility artifact.  Metals may result in incomplete nulling of CSF signal simulating hemorrhage or increased CSF proteins.  This is commonly seen in the frontal regions in patients with dental braces.

References:

1. Cianfoni A, Martin MGM, Hesselink JR, et al. Artifact simulating subarachnoid and intraventricular hemorrhage on single-shot, fast spin-echo fluid-attenuated inversion recovery imaging caused by head movement: a trap for the unwary. AJNR Am J Neuroradiol 2006; 27: 843-849
2. Tha KK, Terae S, Kudo K, Miyasaka K. Differential diagnosis of hyperintense cerebrospinal fluid on fluid-attenuated inversion recovery images of the brain. Part 2: non-pathological conditions. British J Radiol 2009; 82: 610-614

Seven months later the patient re-presented to the ED with persistent waxing and waning hemiparesis, peripheral loss of sensation, and worsening ataxia. MRI at this admission demonstrated resolution of diffusion abnormalities in the left internal capsule but new right hemispheric lesions. The more inferior lesion was associated with restrained diffusion. The bright signal on DWI in the more superior lesion was due to “T2 shine-through”.

FLAIR imaging at the second presentation demonstrated multiple white matter lesions.

There was prominent “ring” enhancement on of the uppermost right hemispheric white matter lesion.

Subsequent clinical evaluation supported a diagnosis of multiple sclerosis.

Discussion:

Lesions of multiple sclerosis may demonstrate diffusion restraint. This does not reliably correlate with acute inflammation and blood brain barrier breakdown, as illustrated by the enhancing lesion with increased ADC in this case. The presenting lesion location and clinical background in this patient led (unsurprisingly) to a diagnosis of lacunar infarction. Her young age (30) might have been a clue to suggest an alternate diagnosis.

References:

1. Karaarslan E, Arslan A. Diffusion weighted MR imaging in non-infarct lesions of the brain. EJR 2007;65:402-16

2. Stadnik TW, Demaerel P, Luypaert RR, et al. Imaging tutorial: Differential diagnosis of bright lesions on diffusion-weighted MR images. Radiographics 2003;23:e7

Dumbell spinal mass: Nerve sheath tumor or something completely different?

A  “dumbell” spinal mass was discovered during CT angiographic evaluation of an aortic aneurysm in this 66-year-old female. She had experienced constant but stable low back pain. There were no neurologic deficits.

Non-contrast axial CT at T11-12

Contrast-enhanced axial CT image at T11-12

Axial T2 weighted image at T11-12

Axial T1 weighted image at T11-12

Axial enhanced T1 weighted image at T11-12

The lesion was biopsied under CT guidance. At pathology, the lesion was composed of closely apposed small to medium sized blood vessels (some of which contained organizing thrombus) without intervening stroma. The vessels were admixed with fibroadipose tissue. The pathological diagnosis was “hemangioma” (a misnomer, as these lesions represent venous vascular malformations, not true hemangiomas). More detailed review of the imaging study revealed several findings that might have suggested this pathologic possibility.

Axial NECT demonstrates a tiny phlebolith (arrow).

Bone window demonstrates honeycomb changes and thickened trabeulae (arrow) in the right transverse process.

FIg. 1 T1 weighted midline sagittal image.

Fig 2 Axial T2-weighted at third ventricular level.

This submission is a 23 year old male patient who became lethargic and somnolent after playing soccer. On physical exam he was somnolent, but arousable with no focal neurologic deficits. An unenhanced CT of the brain initially demonstrated right frontal horn dilatation. A subsequent CT demonstrated bilateral lateral and third ventricular dilatation. Following placement of a ventriculostomy catheter, MRI was obtained and demonstrated a cystic-appearing third ventricular lesion. The lesion was hyperintense on T1WI (Fig 1) and hypointense on T2WI (Fig 2).

During attempted endocscopic removal of the lesion, it was “lost” from the surgical forceps, though a partial specimen was retrieved. Subsequent MR imaging demonstrated that the cyst was now located in the ventricular trigone (Fig 3). At pathology, findings were consistent with a cysticercal cyst. There was no scolex in the specimen.

Fig 3. Axial T1 weighted MR image at level of ventricular atria.

Fig 4. Axial CT at level of the frontal horn. Arrow indicates presumed initial cyst location.

Fig 5. Arrow indicates a right parietal parenchymal calcification.

Interestingly, review of the preoperative CT studies suggested that the cyst had started in the right frontal horn  (Fig 4) and also  revealed a parenchymal calcification (Fig 5), almost certainly an additional manifestation of cysticercosis in this Hispanic patient. Key “hints” to correct identification of this Aunt Mickey case included the parenchymal calcification, cyst mobility, and ethnicity of the patient.

Colloid cysts are the most common lesion of the anterior superior third ventricle. They are of variable signal intensity on T1 and T2 weighted images, presumably reflecting the variable viscosity of proteinaceous cyst contents. Cysts may be CSF-like (dark on T1 and bright on T2), or when more proteinaceous, may appear bright on T1 and dark on T2 weighted images. The occasional similarity of racemose cysts of cysticerosis to colloid cysts has been previously reported. Migration of the cyst has also been reported.

References:

1: Gupta A, Nadimpalli SP, Cavallino RP. Intraventricular neurocysticercosis mimicking colloid cyst. Case report. J Neurosurg. 2002 Jul;97(1):208-10.

2: Wray SD, Ellis TL, Bianco S. Migratory neurocysticercosis mimicking a third ventricular colloid cyst. Case report. J Neurosurg. 2001 Jul;95(1):122-3.

3: Couldwell WT, Chandrasoma P, Apuzzo ML, Zee CS. Third ventricular cysticercal cyst mimicking a colloid cyst: case report. Neurosurgery. 1995 Dec;37(6):1200-3.

4: do Amaral LL, Ferreira RM, da Rocha AJ, Ferreira NP. Neurocysticercosis:Evaluation with advanced magnetic resonance techniques and atypical forms. Top Magn Reson Imaging. 2005 Apr;16(2):127-44.

5: Garcia HH, Del Brutto OH; Cysticercosis Working Group in Peru. Neurocysticercosis: updated concepts about an old disease. Lancet Neurol. 2005 Oct;4(10):653-61.

6: Castillo M. Imaging of neurocysticercosis. Semin Roentgenol. 2004 Oct;39(4):465-73.