Relationship between proprioception at the knee joint and gait ataxia in HSAN III

Background: Hereditary sensory and autonomic neuropathy type III features marked ataxic gait that progressively worsens over time. We assessed whether proprioceptive disturbances can explain the ataxia. Methods: Proprioception at the knee joint was assessed using passive joint angle matching in 18 patients and 14 age-matched controls; 5 patients with cerebellar ataxia were also studied. Ataxia was quantified using the Brief Ataxia Rating Score, which ranged from 7 to 26 of 30. Results: Neuropathy patients performed poorly in judging joint position: mean absolute error was 8.7°±1.0°, and the range was very wide (2.8°-18.1°); conversely, absolute error was only 2.7°±0.3° (1.6°-5.5°) in the controls and 3.0°±0.2° (2.1°-3.4°) in the cerebellar patients. This error was positively correlated to the degree of ataxia in the neuropathy patients but not the cerebellar patients. Conclusions: These results suggest that poor proprioceptive acuity at the knee joint is a major contributor to the ataxic gait associated with hereditary sensory and autonomic neuropathy type III.