SENSORY‐MOTOR POLYNEUROPATHY IN A PATIENT WITH MITOCHONDRIAL MYOPATHY

Benedetti L. 1 , Grandis M.1, Bruno C. 2 , Bado M. 2 , Abruzzese M. 1 , Mancardi G.L. 1 , Schenone A. 11 Department of Neurological Sciences and Vision, University of Genoa, 2 Operative Unit of Neuromuscular Disease, Gaslini Hospital, University of Genoa Mitochondrial myopathy is a multisystem disease with heterogeneous clinical manifestations. The existence of neuropathy has been described in mitochondrial disorders such as MELAS, MERRF, Leigh's syndrome, the Kearns‐Sayre syndrome and progressive external ophthalmoplegia and constitutes a basic component of the NARP (neuropathy, ataxia and retinosis pigmentosa). We describe a 36‐year‐old woman who came to our observation 12 years ago for external ophthalmoplegia and bilateral ptosis. Morphological examination of a muscle biopsy suggested a mitochondrial myopathy. Genetic studies ruled out the typical mitochondrial DNA‐mutations. One year ago she started to complain of acral paresthesias and gait imbalance. Neurological examination revealed, besides the signs of a myopathy, reduced tendon reflexes, distal sensory impairment and a positive Romberg sign. Nerve conduction studies showed mild slowing of motor conduction velocity on right and left peroneal nerves, with normal amplitude of cMAP, and mild to severe slowing of sensory conduction velocity on both sural nerves, with reduced amplitude of SAP. Therefore a predominantly sensory‐ataxic neuropathy was diagnosed. A polyneuropathy may be a common finding in mitochondrial disorders and is probably underdiagnosed. Since the onset of neuropathic symptoms and signs may follow the diagnosis of mitochondrial myopathy, nerve conduction velocity studies could be of help in disclosing subclinical cases.