Stiff Person Syndrome (SPS) - Diagnosis and Management Summary



Epidemiology:

 • Prevalence: 1-2 cases per million - rare

 • Age 20-50, Females 2-3 times than men

 • Commonly associated with DM-1, thyroiditis, vitiligo, and pernicious anemia



Stiff Person Syndrome Pathophysiology:

 • Associated with autoimmunity

 • Research indicates that it is the result of an autoimmune response gone awry in the brain and spinal cord.



Clinical Manifestations of Stiff Person Syndrome:

 • Progressive muscle stiffness, rigidity, spasm - axial muscles

 • Severely impaired ambulation

 • Excessive muscle rigidity - lumbar, trunk, proximal muscles - sustained muscle contractions (agonist and antagonist muscles)

 • Wide based gait with tendency to fall

 • Triggers - sudden movement, noise, emotional upset

 • Spasms - visualized-tight, rock-hard, board-like feel

 • Autonomic dysfunction - hyperpyrexia, diaphoresis, high HR

 • Sudden death - diaphragm spasm - apnea



Stiff Person Syndrome - Diagnosis:

 • High index of suspicion

 • Presence of:

	- Stiffness in axial and limb muscles resulting in impairment of ambulation

	- Presence of superimposed spasms triggered by noise, movement or emotions

	- A positive therapeutic response to diazepam or findings of continuous motor unit activity on EMG

	- Absence of other neurological disorders

 • Testing anti-GAD (positive in 2/3 of pts)

 • Therapeutic trial of diazepam

 • EMG testing



Lab Findings in Stiff Person Syndrome:

 • Anti-GAD Ab (>1000u/ml)

	- People with SPS have elevated levels of GAD, an antibody that works against an enzyme involved in the synthesis of an important neurotransmitter in the brain.

 • CSF: Oligoclonal bands

 • Normal ESR, CRP

 • Other autoantibodies - TPO, TTG, etc



EMG Studies:

 • Continuous motor-unit activity, typically decreased by diazepam, sleep



DDx:

 • Neuromyotonia, Tetanus, Strychnine poisoning, Parkinson's disease, Multiple sclerosis, Ankylosing spondylitis, Axial dystonia, Focal limb or joint disorders, Fibromyalgia, Psychosomatic illness, Anxiety, Phobia



Stiff Person Syndrome Treatment:

 • Initial/Symptomatic Therapy:

	- BDZ: Diazepam or clonazepam

 • Resistant to Initial Symptomatic Therapy:

	- Baclofen

 • Severe Disease/Resistant:

	- IVIG

	- If Resistant to IVIG: Rituximab (anti-CD20), plasma exchange, or others (botox, sodium valproate, vigabatrin, propofol)



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