Sensory neuronopathy in ataxia with oculomotor apraxia type 2

The objective of this article has been to describe the presence of a sensory neuronopathy in a patient harbouring ataxia with oculomotor apraxia type 2 (AOA2). A 40 year-old woman, born to consanguineous parents, presented with ataxia, decreased vibration sense, areflexia, indifferent plantar responses, preserved muscle volume and strength, and oculomotor apraxia; elevated levels of serum alpha-fetoprotein and creatine-kinase were found. A homozygous missense mutation, causing a substitution of a molecule of arginine for histidine at the helicase domain of the senataxin protein, was found. Two electrophysiological studies were performed, in which decreased amplitudes of the sensory action potentials were followed some years later by an absence of sensory action potentials in the lower limbs, and increased latencies in the somatosensory evoked potentials. Motor nerve conduction velocities were normal, and electromyographic recordings did not show abnormalities. Taken together, these findings are suggestive of a progressive sensory neuronopathy. The patterns of neuromuscular disturbance in AOA2 have not been thoroughly defined; therefore, a sensory neuronopathy should be considered part of the spectrum of neuromuscular manifestations in this disease. Genetic analysis may be of help to diagnose cases with unusual neuromuscular characteristics, like the one presented here.