Proximally evoked soleus H-reflex to S1 nerve root stimulation in sensory neuronopathies (ganglionopathies).

ABSTRACT

INTRODUCTION: Sensory neuronopathy (SNN) mimics distal sensory axonopathy. The conventional H-reflex elicited by tibial nerve stimulation (tibial H-reflex) is usually abnormal in both conditions. We evaluated the proximally evoked soleus H-reflex in response to S1 nerve root stimulation (S1 foramen H-reflex) in SNN. METHODS: Eleven patients with SNN and 6 with distal sensory axonopathy were studied. Tibial and S1 foramen H-reflexes were performed bilaterally in each patient. RESULTS: Tibial and S1 foramen H-reflexes were absent bilaterally in all patients with SNN. In the patients with distal sensory axonopathy, tibial H-reflexes were absent in 4 and demonstrated prolonged latencies in 2, but S1 foramen H-reflexes were normal. CONCLUSIONS: Characteristic absence of the H-reflex after both proximal and distal stimulation reflects primary loss of dorsal root ganglion (DRG) neurons and the distinct non-length-dependent impairment of sensory nerve fibers in SNN.