We describe an interesting imaging finding in two patients, one with chronic inflammatory demyelinating polyneuropathy (CIDP) and the other having neurofibromatosis. The trigeminal nerves were hypertrophied, giving the appearance of a moustache-'the moustache sign'.
Case 1A 17-year-old girl presented with subacute, fluctuating, distal and proximal limb weakness, distal hypoesthesia, and generalized areflexia. Electrophysiology confirmed demyelination with multifocal conduction blocks at nonentrapment sites in all four limbs. Cerebrospinal fluid examination showed albumin-cytological dissociation. Magnetic resonance imaging (MRI) revealed bilateral thickening and enhancement of cisternal segment and all three divisions (ophthalmic, maxillary, and mandibular) of the trigeminal nerve [ Figure 1]. Spinal roots were hypertrophied as well. Cranial nerve hypertrophy is seen in 11-57% patients with CIDP. [1] Case 2 A 30-year-old male presented with sensory ataxia, areflexia, distal weakness, and wasting of all four limbs. MRI showed multiple intraspinal schwannomas, m e n i n g i o m a s , e p e n d y m o m a s , a n d b i l a t e r a l vestibular schwannomas. The trigeminal nerves were thickened [ Figure 2].Besides these two causes, trigeminal nerve may be enlarged in the following conditions: (1) Figure 1: Coronal short tau inversion recovery image showing trigeminal nerve in the Meckel's cave and its maxillary division as it exits foramen ovale. The nerve is thickened and giving the appearance of 'moustache' Figure 2: T1 weighted magnetic resonance imaging with contrast showing enlargement of trigeminal nerves due to schwannomas giving the appearance of the 'moustache' Neuroimage
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