Objective:

Analyze gait in GAD65 neurologic autoimmunity. 

Background:

GAD65 neurologic autoimmunity manifestations include stiff person spectrum disorder (SPSD), ataxia, and epilepsy. Seizure frequency and cognitive testing are used as outcome measures in epilepsy, but documenting functional changes in SPSD and ataxia is more challenging, complicating treatment decisions and outcome tracking in therapeutic trials.

Design/Methods:

Patients with high-titer GAD65 antibodies and associated neurologic syndrome seen in the Mayo Autoimmune Neurology Clinic underwent timed 25-foot walk (T25FW) and gait analysis using APDM Opal devices on wrists, ankles, sternum, and lumbar spine.

Results:

Seventeen patients with GAD65 neurologic autoimmunity (median serum concentration 515 nmol/L [28.5 –1880]; CSF 1.5 nmol/L [ 0.65 – 12.8]) were included: 9 with SPSD, 6 with ataxia, and 2 with epilepsy (controls); 9/17 were female. Analysis was performed at median age 56 years (range 21 – 82), 49 months from diagnosis (0 – 344). T25FW was 9.3s (6.4 – 20.5) for SPSD, 14.8s (8.8 – 17.7) for ataxia, and 7.1 s (6.8 – 7.3; p=0.06) for epilepsy patients. Stride length was shorter in patients with ataxia (0.7 m [0.5-1.0]) relative to SPSD (0.9 m [0.6 – 1.2]) and epilepsy (1.1 m [1.1-1.2]). Double support time was highest in ataxia (34.3%, [27.0 – 41.8], p=0.02) compared to SPSD (23.4% [21.2 – 38.2]) and epilepsy (22.8% [22.5 – 23.2]). Toe off angle was lower in ataxia (24.7 degrees [14.2 – 31.2]) and SPSD (26.8 degrees [17.6 – 30.8]) relative to epilepsy (37.0 [35.0 – 39.0]). Coronal plane lumbar spine range of motion was reduced in those with SPSD (3.41 degrees, [2.0 – 5.3]) and ataxia (3.8 degrees [2.1 – 10.3]) compared to epilepsy (8.8 degrees [8.2 – 9.4]).

Conclusions:

Wearable gait analysis offers quantitative assessment of functional changes in GAD65-associated SPSD and ataxia. Longitudinal data are needed to identify metrics sensitive to treatment response and progression.