Brain Pathology Case of the Month - June 1997

Contributed by D.A. DeRubeis, J. Woulfe, D. Rosso, S. Lownie, L. Parnes, D. Lee, M.J. Strong, R.R. Hammond
-- University of Western Ontario, London, Ontario, Canada


This 42 year old R handed male presented with an eight week history of progressive left lower motor neuron facial weakness. There was no history of recent viral illness or other constitutional symptoms. There had been no recent trauma or nasal discharge. No recent foreign travel had occured and he had no risk factors for HIV infection. He did not report headache, hearing loss, tinnitus, abnormalities of taste or smell, decreased visual acuity, dysphagia or dysarthria. He had no history of neurofibromatosis or malignancy.

The general physical examination was normal. Neurological examination showed a left lower motor neuron facial weakness and left periocular fasciculations. His fundi and visual fields were normal. There was decreased sensation to pin prick in the distribution of left infra-orbital branch of the trigeminal nerve. The motor branch of the trigeminal was intact. Corneal sensation was intact. The external auditory canal was normal and hearing was preserved. Cranial nerves nine through twelve were intact. Bulk, power and tone were normal. Reflexes were symmetric and the toes were downgoing. There were no cerebellar deficits. Primary and secondary sensory modalities were intact. Gait was normal.

Laboratory investigations including CBC, electrolytes, BUN, Creatinine, ANA, complement, lyme serology, ACE levels and TB skin test were normal. Cerebrospinal fluid was normal. CSF cultures and oligoclonal banding were negative. A chest x-ray was normal. EMG and nerve conduction studies showed a conduction block peripherally in the left facial nerve. Post-gadolinium enhanced MRI examination demonstrated enhancement of the descending portion of the left seventh cranial nerve just distal to the ganglion. No other temporal bone or intracranial pathologies were seen. The muscles of mastication were symmetric. A provisional diagnosis of idiopathic Bell's palsy was made and there was mild transient improvement in the facial weakness with a short course of prednisone.

One year after the onset of symptoms, he had a complete lower motor neuron left seventh nerve palsy. Hearing remained normal without hyperacusis and the external auditory canal was unremarkable. There was decreased bulk of the left masseter muscle and he had difficulty fully opening the jaw. Sensation was reduced in the third division of the left trigeminal nerve. Repeat chest x-ray, CSF examinations and ACE levels were normal. Two courses of immune globulin were given because of concern for the possibility of a conduction block neuropathy or chronic inflammatory demyelinating polyneuropathy. There was no improvement.

Repeat MRI revealed extension of the left seventh cranial nerve enhancement from the genu to the proximal parotid segment. Axial contrast enhancing images show enhancing lesions expanding the left cavernous sinus (arrows) and the the facial nerve genu (F) (Image 01). There was also intense enhancement of the left trigeminal ganglion extending extracranially along an enlarged mandibular division (Image 02). This was accompanied by infiltration of the left pterygoid muscles. The proximal second division of the left trigeminal nerve was thickened and enhancing. There were no bony lesions seen and the basal meninges were normal.

The patient was brought to the operating room for exploration of the facial canal and biopsy of the lesion. Following the initial diagnostic biopsy, a 2-stage gross total resection was carried out with removal of the following structures: trigeminal nerve (sensory and motor roots at their origin on the pons), gasserian ganglion, proximal parts of V2 and V3, greater superficial petrosal nerve, geniculate ganglion, inferior alveolar, lingual and mental nerves. The parotid gland was removed as well as many fine branches of VII. Other fine distal branches of V2 and V3 were suspected to be involved. These fields were subsequently irradiated (6000 cGy in 30 fractions). In summary, there was gross total removal of tumour from the intracranial compartment and from the infratemporal fossa.




International Society of Neuropathology