Cranial nerve deficits due to amyloidosis associated with plasma cell dyscrasia

Cranial nerve dysfunction is exceedingly rare in amyloidosis. Cranial nerve deficits have been described in the very rare form of familial amyloidosis in which there appears to be an autosomal dominant pattern of inheritance. By contrast, they are virtually unreported in the two common forms of amyloidosis, that is, secondary amyloidosis (AA), usually associated with a chronic inflammatory lesion, and primary amyloidosis (AL), resulting from light-chain immunoglobulins of plasma cell dyscrasias. Although neurologic involvement in these forms of amyloidosis has been reported in the peripheral nerves, spinal nerve roots, and autonomic ganglia, the absence of reports of cranial nerve lesions is remarkable. We report the case of a woman with multiple bilateral cranial nerve deficits involving the left trigeminal, left facial, right abducens, and hypoglossal nerves. She had nonfamilial amyloidosis associated with a plasma cell dyscrasia of the IgG kappa type with increased production of light-chain immunoglobulins. The rarity of cranial nerve involvement in this clinical setting is highlighted by three previous studies, each of which reported involvement of only a single nerve (either the facial or olfactory nerve). Since aging has been correlated with congophilic changes in the brain, the explanation for the sparing of cranial nerves can be only speculative.