Objective: To describe a case of Stiff-Limb Syndrome with ataxic features which had delayed EMG findings and improvement to IVIG.

Background: Stiff-Person Syndrome (SPS) is part of a spectrum of progressive autoimmune neurological diseases that also include isolated cerebellar ataxias, progressive encephalomyelitis with rigidity and myoclonus (PERM), epilepsy, and autoimmune dementia. Stiff-Limb Syndrome (SLS) is differentiated from SPS clinically through the isolated involvement of appendicular muscle groups and early sparing of paraspinal musculature. Barker, et al. described SLS patients as having rigidity, painful spasms, and abnormal postures of the distal limb, with developing sphincter or brainstem involvement and almost none having generalized myoclonic jerks or truncal spasms. Prognosis is poor for SLS patients with many becoming wheelchair dependent.    

Methods: Case Report

Results: A 52-year-old woman with history of pernicious anemia and B12 deficiency, and a family history of autoimmunity, presented with two months of axial ataxia, lower back pain, and unsteady gait. She was hospitalized after a fall and found to have a low B12 of 178 ng/mL with a normal copper level. She was given intramuscular B12 supplementation, physical therapy, but with no improvement. Neurological examination showed considerable bilateral leg spasticity to passive movement, truncal titubation, and a bilateral intention tremor and dysmetria of her arms. Initial EMG was normal but repeat EMG, three months later, demonstrated spontaneous, continuous motor unit action potentials with normal morphology in the left tibialis anterior only occurring while patient was relaxed. Glutamic Acid Decarboxylase antibody (GAD-65) was positive at 30.0 U/mL (Reference range <=1.0 U/mL). Medication trials with benzodiazepines, baclofen, pregabalin, dantrolene, and gabapentin were not effective. IVIG was initiated with dramatic improvement in pain but no improvement in spasticity or gait until she completed 10 trials. After her 12th consecutive dose of IVIG, she has considerable improvement in spasticity and gait and was able to return to work full time.  

Conclusions: Our patient is unique as she had mild ataxia, no dystonia, and delayed unilateral, positive EMG findings. She had a tremendous recovery and returned to full time nursing duty. The exact duration of treatment is still unknown and further research into the long-term prognosis of SLS is needed. 

References: Sarva H, Deik A, Ullah A, Severt WL. Clinical spectrum of stiff person syndrome: A review of recent reports. Tremor and Other Hyperkinetic Movements 2016;6:340. doi:10.7916/D85M65GD.

Barker RA, Revesz T, Thom M, Marsden CD, Brown P. Review of 23 patients affected by the stiff man syndrome: clinical subdivision into stiff trunk (man) syndrome, stiff limb syndrome, and progressive encephalomyelitis with rigidity. J Neurol Neurosurg Psychiatry 1998;65:633–640.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/stiff-limb-syndrome-with-cerebellar-features-and-atypical-emg-findings-responds-to-ivig/