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Neurological Rehabilitation

IncobotulinumtoxinA in Treating Muscle Spasms Associated with Stiff Limb Syndrome: A Case Report

Friday, October 24, 2025
12:00 PM - 1:30 PM MT
Location: Kiosk 6

    Primary Author(s)

  • John Jung, MD

    House Officer: PGY-3
    University of Michigan Health System PM&R Program
    Ann Arbor, Michigan

    • Co-Author(s)

  • Jared Gershowitz, DO

    House Officer: PGY 4
    University of Michigan Health System PM&R Program
    Ann Arbor, Michigan

  • RN

    Reina Nakamura, DO

    Assistant Professor
    University of Michigan
    Ann Arbor, Michigan

Disclosure(s):
John Jung, MD: No financial relationships to disclose
Jared Gershowitz, DO: No financial relationships to disclose
Case Diagnosis: A 54-year-old patient with latent autoimmune diabetes (LADA) developed burning pain along the left dorsal foot and global tightness in the left lower extremity (LLE) diagnosed with stiff limb syndrome.

Case Description or Program Description: Physical exam was notable for inability to relax the left leg and foot. Workup showed unremarkable cervical and thoracic MRI, labs (Vitamin B12, Human T-cell lymphotropic virus, Copper, Vitamin E ), elevated creatine kinase (519) and Glutamic acid decarboxylase 65 (537 nmol/L). On electromyography, there was an absent superficial peroneal response with normal motor unit potential in morphology and recruitment pattern. There was difficulty with assessment of muscles of the LLE at rest due to continuous muscle activation concerning for a hyperexcitability syndrome. The patient was referred to neuromuscular specialists and diagnosed with stiff limb syndrome (SLS), a variant of stiff person syndrome (SPS).

Setting: Outpatient Clinic, Tertiary Care Hospital

Assessment/Results: The patient was started on baclofen and diazepam but continued to experience stiffness despite titration. 10 treatments of Intravenous immunoglobulin showed no significant improvement and was discontinued due to a refractory course complicated by hemolytic anemia. Rituximab also provided no benefit. Due to persistent stiffness and spasms isolated to the LLE, IncobotulinumtoxinA was trialed, resulting in functional improvement and better ambulation with a cane.

Discussion (relevance): Stiff limb syndrome, a variant of SPS, primarily affects distal limbs, causing rigidity, spasms, and abnormal postures. Unlike SPS, SLS rarely involves trunk muscles. SLS may be associated with autoimmune diseases like type 1 diabetes and LADA, with high anti-Glutamic Acid Decarboxylase (GAD) Antibodies titers strongly suggestive of this disease. This case illustrates the clinical utility of IncobotulinumtoxinA in treating muscle spasms associated with SLS.

Conclusions: SLS is rare and should be considered in the differential diagnosis of muscle stiffness in patients with LADA. Though chronic and progressive, targeted therapies including IncobotulinumtoxinA can significantly improve quality of life.