We describe a case of multiple sclerosis with bilateral trigeminal nerve root involvement at presentation and discuss probable mechanisms.  

In MS, trigeminal nerve root enhancement is usually associated with a lesion in the root entry zone. Nerve root enhancement without root entry zone lesion is rarely encountered in clinical practice. 

A 27-year-old Hispanic female presented with a 3-week history of gait imbalance, vertigo, and paresthesia of the face followed by right eye vision loss. MRI of the brain and spinal cord showed contrast enhancement in the right optic nerve. In addition, active demyelination with incomplete ring pattern was demonstrated in the cervical spinal cord as well as active lesions in the brainstem, corpus callosum, and juxtacortical region. Contrast enhancement was observed in trigeminal nerve roots. CSF showed 28 WBCs and unique oligoclonal bands. Extensive workup showed no other etiology. The patient was treated with methylprednisolone and plasma exchange followed by near full recovery at 6 months. A follow-up MRI at 4 months showed resolution of contrast enhancement and no new lesions. Repeat CSF analysis at 6 months showed no pleocytosis but persistence of oligoclonal bands.

Trigeminal nerve root enhancement in MS is seldom described in the literature. Nerve root enhancement in the absence of root entry zone lesion may be asymptomatic or symptomatic. Several mechanisms are hypothesized. The CNS myelin of the trigeminal nerve extends up to 5 mm from the root entry. Nerve enhancement beyond this may suggest cross-reactivity with peripheral myelin as suggested by reports of polyradiculitis in MS patients and CNS involvement in inflammatory polyradiculitis.

In our case, MRI evolution of demyelinating lesions, persistence of OCBs and exclusion of alternative etiologies established the diagnosis of MS.  Infectious and other inflammatory etiologies should carefully be excluded in such cases before MS diagnosis is established.