Spinal schwannoma

Findings

61-year-old male with a multilevel intradural extramedullary lesion demonstrating isointensity on sagittal T1 (Figure 1), intense enhancement on sagittal T1 post gad (Figure 2) and sagittal T1 post gad fat sat (Figure 3), and high signal intensity on sag STIR (Figure 4).
Axial T1 pre contrast (Figure 5) post contrast (Figure 6) and post contrast with fat saturation (Figure 7) demonstrate an intradural extramedullary lesion compressing and displacing the thoracic cord to the left.

Differential diagnosis for intradural-extramedullary spinal mass lesions:
- Nerve sheath tumor
- Meningioma
- Metastasis
- Paraganglioma
- Vascular malformations
- Inflammatory process
- Developmental lesions


Diagnosis: Spinal schwannoma


Nerve sheath tumors and meningiomas are the two most common intradural-extramedullary spinal tumors, representing 30 and 25% of presenting lesions, respectively. Both are typically benign, slow-growing tumors which may be present for years before there is functional impairment. MRI is the modality of choice in distinguishing these pathologies.

Nerve sheath tumors compromise schwannomas and neurofibromas, most often present in the fourth and fifth decades of life, and may be associated with neurofibromatosis. Schwannomas arise from dorsal sensory roots, more commonly in the lower thoracic and lumbar areas. Neurofibromas, unlike schwannomas, involve the parent nerve, and are unencapsulated.

Meningiomas are the second most common intradural-extramedullary spinal tumor and are more common in women. Multiple meningiomas may also be associated with neurofibromatosis. Meningiomas are predominately located in the upper and mid- thoracic areas, different from schwannomas, but are in a similar distribution in the anterior-posterior plane. Both nerve sheath tumors and meningiomas can be found in a “dumbbell shape,” with both extra- and intradural components.

MRI is the modality of choice in the evaluation of intradural-extramedullary spinal tumors. Nerve sheath tumors and meningiomas demonstrate characteristics of craniocaudal location divergence, hyperintensity and heterogeneity of T2W images, intensity and heterogeneity of enhancement, and the presence or absence of the “dural tail sign”. Schwannomas are typically hyperintense and heterogeneous compared to meningiomas on T2W images. The tumors show different contrast enhancement- meningiomas enhance moderately and homogenously, while schwannomas enhance strongly and irregularly. The “dural tail sign,” a reactive thickening of dura tapering away from the tumor, is associated with meningiomas, though this is not a specific sign. Additionally, neural foraminal extension and foraminal widening is suggestive of schwannoma, while bony sclerosis surrounding the mass is suggestive of meningioma.
Vascular tumors may necessitate pre-operative angiography and embolization.

Type II spinal AVM

Findings

MRI Spine Thoracic: Focal area of low T2 signal with in the spinal cord at the T7 level. There is increased T2 signal within the surrounding cord without mass effect. No clearly abnormal T1 signal or enhancement is seen. No abnormal flow voids are present.
CT Chest: There is a tortuous vessel within the posterior spinal canal which enters at the T9-T10 level from the right and terminates in a blush of contrast at the T7 level in the spinal cord.
Angiogram: T8 arterial injection shows an abnormal vessel extending superiorly to the T7 level with a small nest of abnormal vessels and a very early draining vein which extends inferiorly to the T9-10 level.

Differential diagnosis:
- Cavernous angioma
- Ependymoma
- AVM
- AVF


Diagnosis: Type II spinal AVM


Key points

There are four types of spinal AVMs, this is a type II which means there is abnormal intramedullary vasculature with a nidus. Type III lesions are also true AVMs; they are just larger and more complex. Type I and IV lesions are actually AVFs. Type I is the most common spinal AVM; it is a dural arteriovenous fistula. Type IV is an intradural extramedullary AVF from spinal artery to the coronal venous plexus.
Type II AVMs are generally diagnosed in the early 20s. Patients have a progressive course of myelopathy with severe sudden neurologic deficits when the lesions hemorrhage. Males and females are equally affected.
MRI is very useful in localizing the lesion. A definitive diagnosis is difficult as in this case if the vessels are too small to be visualized. Angiography is the gold standard for making the diagnosis. Both CT and MRI can help with angiogram planning.
Treatment is often embolization with good responses; however, the lesions can return. Surgery is often performed in order to prevent reoccurrence of the lesion.

Uncal herniation with posterior cerebral artery occlusion and resulting infarct

Findings

Image 1: Acute intraparenchymal hemorrhage with midline shift.
Image 2: Effacement of the basal cistern, quadrigeminal plate with enlargement of the contralateral lateral ventricle.
Image 3: Followup study 2 weeks later demonstrates hypo density in the left posterior cerebral artery distribution.

Differential diagnosis:
- Uncal herniation with posterior cerebral artery occlusion
- New thrombotic infarct in the posterior cerebral artery distribution
- Edema from infarct not seen with initial imaging


Diagnosis: Uncal herniation with posterior cerebral artery occlusion and resulting infarct


Discussion

With increased intracranial pressure, the brain can herniate transtentorially, cutting off circulation to the posterior cerebral artery and causing infarct of the ipsilateral occipital lobe. Radiologic evidence of descending transtentorial herniation includes obstruction of the CSF draining system and contralateral enlargement of the lateral ventricle, the uncus extending into the suprasellar cistern, and ipsilateral prepontine cistern widening. The clinical evidence for herniation itself includes an ipsilateral dilated pupil and contralateral hemiparesis, though these may be difficult to discern in the setting of already increased intracranial pressure due to the underlying etiology. The sequelae of PCA infarct include acute vision loss, confusion, new onset posterior cranium headache, paresthesias, limb weakness, dizziness, nausea, memory loss and language dysfunction.


Radiologic overview of the diagnosis

There will be evidence for increased intracranial pressure such as a space-occupying lesion, hemorrhage or edema; and, more specifically, evidence for transtentorial herniation including mass effect with uncal extension into the suprasellar cistern and contralateral lateral ventricle expansion. Over a period of time, there will eventually develop ipsilateral or bilateral signs of infarct on MR or CT in the distribution of the posterior cerebral artery within the occipital lobe.

Frontal sinus mucocele

Findings

There is a large, expansile mass in the right frontal sinus crossing the midline, measuring 2.3 x 5.7 x 3.8 cm (AP, transverse, cephalocaudad dimensions). This mass extends inferiorly into the right orbit, pushing the right globe inferiorly and anteriorly. There is discontinuity of the ethmoidal margin. However, there is no definite extension of the mass into the brain parenchyma. These findings are consistent with a frontal sinus mucocele. Also noted is extensive sinus disease involving the other visualized paranasal sinuses.


Diagnosis: Frontal sinus mucocele


A mucocele is an encapsulated fluid collection which occurs due to obstruction of a paranasal sinus ostium. Obstruction of a sinus ostium can occur secondary to chronic sinus inflammation, trauma, surgery, chronic sinus polyposis and tumors such as an osteoma. In children, there may be a history of cystic fibrosis.

Mucoceles are important diagnoses to make due to their expansile nature. They have the ability to erode through adjacent bones, including the base of the skull to result in intracranial extension. Mucoceles can also involve the orbital cavity, resulting in proptosis and displacement of the globe. Orbital involvement may also affect branches of cranial nerve III. They can become inflamed and fill with pus (pyocele) or pus and mucus (mucopyocele). Clinically, patients experience symptoms which occur as a result of localized mass effect and inflammation. Depending on the extent of the mucocele and the paranasal sinus affected, patients may present with intractable headaches, orbital discomfort, decreased visual acuity, a visual field defect, and facial pain.

Plain film radiographs of the sinuses will reveal smooth, expansile enlargement of the affected paranasal sinus. The adjacent bone may also be thinned secondary to the expansile nature of the lesion. The sinus is typically completely opacified. Further work-up includes a CT of the maxillofacial bones, which will reveal a uniform non-enhancing, low-attenuating expansile mass in the paranasal sinus. There may be regions of hyperdensity within the lesion representing inspissated mucus. There may also be bone remodeling and thinning but without evidence for bone destruction. T1-weighted MR images depict mucoceles as an expansile and hyperintense abnormality of the affected paranasal sinus. T2-weighted MR images further characterize a mucocele as a hyperintense lesion with greater signal intensity than that seen on the T1-weighted images. The signal intensity will further depend on the state of hydration and contents within the mucocele (protein, hemorrhage, and calcification).

The preferred treatment of mucoceles is surgery with sinus reconstruction. Surgical treatment includes conservative options (marsupialization of the mucocele) and radical options (removal of the mucosa and obliteration of the sinus). If possible, it is important to re-establish sinus drainage to prevent mucocele recurrence. The resected mucosa may be normal or demonstrate areas of squamous metaplasia. Endoscopic sinus surgery has played a larger role in management of mucoceles in recent years. Despite surgery, mucoceles often recur, warranting long-term follow-up.

Dysembryoplastic neuroepithelial tumor (DNET)

Findings

Brain MRI shows T2 hyper intense lesion in a right parietal cortex with multiple small "cystic" components, extension into subcortical white matter. FLAIR hyperintense, but without perilesional edema or mass effect. No contrast enhancement.


Diagnosis: Dysembryoplastic neuroepithelial tumor (DNET)


Key points

Benign intracortical mass, superimposed on a background of cortical dysplasia.
Typical appearance: small, wedge-shaped "bubbly" mass which is based in a single gyrus, extends towards the ventricle. Characteristic features are a lack of mass effect, surrounding edema, or post-contrast enhancement. There should be little/no growth of the lesion over time.
Frequently scallops inner table of skull, sometimes calcifies, and infrequently hemorrhages. Associated cortical dysplasia is common.
Usually found in children/adolescents, comprises 1-2% of primary brain tumors (age <20). Patients commonly present with partial seizures. Most commonly location is in temporal lobe, followed by parietal cortex, caudate nucleus, septum pellucidum. From 5-80% of epilepsy brain specimens show DNETs.


Radiographic Findings

CT: Thickened gyrus, slightly hypo attenuating. May mimic acute ischemia.
MR: T1 - hypo intense with gyral architectural distortion. T2 - strikingly hyper intense, with bubbly cystic components, extends towards ventricle. FLAIR - characteristic "bright rim," but no perilesional edema. T1+C = minimal / no enhancement. DWI = no diffusion restriction.

Choroid plexus papilloma

Findings

MRI imaging demonstrates a large, 7 x 4 x 4 cm (craniocaudal, AP, and transverse) heterogeneous mass within the 4th ventricle, with associated marked obstructive hydrocephalus. This mass extends below the 4th ventricle into the foramen magnum. There is no significant surrounding cerebellar edema.


Diagnosis: Choroid plexus papilloma (pathologically proven)


Key points

Choroid plexus papilloma is a relatively rare pediatric intracranial neoplasm, accounting for approximately 3% of such tumors.
Most common in patients under 1 year of age, and more common in males.
Arise from cuboidal epithelium of choroid plexus.
Associated with Li-Fraumeni and von Hippel Lindau syndromes.
Increased intracranial pressure can result from both tumor secretion of CSF, as well as by CSF outflow obstruction due to the intraventricular mass.
Presenting symptoms may include headache, N/V, ataxia, visual changes, or drowsiness.
On CT and MR, typical findings include a heterogeneously enhancing mass, potentially with cystic areas. On CT, punctuate calcifications may be seen in up to 20% of cases.
Treatment is typically by attempted total resection.

Semilobar holoprosencephaly

Findings

Partial formation of the interhemispheric fissure and falx cerebri in the posterior portions of the brain. Fusion of the frontal lobes. Rudimentary temporal horns of the lateral ventricles. Absent septum pellucidum. Lack of a corpus callosum genu or anterior body. Partial fusion of the thalamus and caudate and hypothalamus are not clearly separated resulting in a small third ventricle.


Diagnosis: Semilobar holoprosencephaly


Key points

There are three types of holoprosencephaly: alobar, semilobar, and lobar.
Semilobar holoprosencephaly represents a congenital brain malformation with severity between alobar and lobar holoprosencephaly.
Clinical findings include microcephaly, macrocephaly, developmental delay, spasticity, or other motor abnormalities.
Imaging findings: Interhemispheric fissure and falx cerebri are partially formed posteriorly, and the anterior portions of the brain are fused and underdeveloped. Septum pellucidum is absent. The splenium of the corpus callosum is present with absence anteriorly of the genu. Anterior extent of corpus callosum formation correlates with remainder of the brain's formation. The hypothalami, caudate, and thalami are partially unseparated resulting in a small 3rd ventricle. Dorsal cysts may be seen, always when the thalami are fused.