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Neuroradiology Case of the Month

October 2001

Clinical Presentation: Patient is a 20-year-old Caucasian female with a history of neurofibromatosis type 2 (NF2), surgical resection of a vestibular and optical nerve schwannomas, dermal neurofibromatosis, bilateral cataracts, and loss of hearing in the left ear secondary to damage to the cochlear nerve. The patient’s family history is significant for a father and brother with NF2

Radiographic Findings: T1-weighted images with gadolinium demonstrate an enhancing lesion in the right cerebellopontine angle extending into the right auditory canal. This lesion exerts a mass effect on the right aspect of the brainstem, causing distortion of the forth ventricle. A smaller enhancing intracanalicular lesion can also be seen on the left side. These enhancing lesions are consistent with bilateral acoustic schwannomas. A small extra-axial enhancing lesion, which is most likely a meningioma, is noted on the anterior aspect of the right frontal lobe. Sagittal T1-weighted images with gadolinium also show a fourth enhancing lesion seen in posterior aspect of the medulla, just caudal to the cerebellum. This lesion is either a schwannoma, ependymoma, or low-grade astrocytoma.

Diagnosis: Neurofibromatosis type 2

Figure 1. Axial and coronal T1-weighted images with gadolinium demonstrating bilateral acoustic schwannomas.
Figure 2. Coronal T1 with gadolinium showing extra-axial meningioma located in right frontal cortex (left) and sagittal T1 with gadolinium showing small enhancing lesion on the posterior aspect of the medulla (right).

Discussion: NF2 is an uncommon, inherited autosomal dominant syndrome associated with an abnormality in chromosome 22 [1]. It is characterized by a propensity to form multiple schwannomas, meningiomas, and ependymomas [1]. The hallmark of NF2 is the presence of bilateral acoustic schwannomas [1]. Schwannomas may also occur along other cranial nerves [2]. Meningiomas typically develop intraventricularly in the choroid plexus, in the sphenoid ridge, olfactory groove or along intracranial nerves [3]. Schwannomas and meningiomas both enhance brightly after administration of contrast [3]. Smaller tumors are often identified on post-contrast studies [3].

Spinal manifestations most commonly include multiple paraspinal schwannomas, meningiomas and ependymomas [3]. All of these tumors enhance uniformly after administration of contrast [3]. Meningiomas are most common within the thoracic region. They are isointense on short and long TR sequences, whereas schwannomas are isointense on short TR sequences but hyperintense on long TR sequences [3]. Ependymomas usually exhibit sharply demarcated borders compared to astrocytomas [3]. Syringohydromyelia may also occur secondary to an intradural or extramedullary mass which disturbs normal CSF flow within the spinal cord [3].

The differential for tumors found in the cerebellopontine angle include schwannomas, meningiomas, ependymomas, basilar artery aneurysm, choroid plexus papillomas, astrocytomas and metastatic disease [2]. Epidermoid and arachnoid cysts do not enhance since they are largely avascular [3]. However, with the strong family history, presence of neurofibromas, and bilateral cataracts, this patient undoubtably has NF2.

Reference

1. Martuza RL, Eldrige R. Neurofibromatosis 2. N Engl J Med, 1988. vol 318(11): 684-688
2. Dahnert, Wolfgang. Radiology Review Manual. Williams and Wilkins, 1998. pg. 137, 170-171, 233.
3. Barkovich, A. James. Pediatric Neuroimaging. Raven Press, 1995. pg. 292-296.