Synonyms:
formerly stiff man syndrome a.k.a. Moersch-Woltmann syndrome
Diagnosis:
Clinical and electrophysiological features, supplemented by antibody tests
Diagnosis by exclusion: Absence of any other neurologic disease or chronic pain syndromes that could explain stiffness and rigidity.
This condition is often mis-diagnosed as psychogenic dystonia
Clinical features:
Rigidity: Insidious onset, Limbs and axial (trunk) muscles, most prominent in the abdominal and thoracolumbar paraspinals. Difficulty in turning or bending
+Continuous co-contraction of agonist and antagonist muscles. With inability to relax:
- Confirmed clinically and electrophysiologically
- +Episodic spasms:
- Superimposed on rigidity
- Precipitated by unexpected noises, tactile stimuli, or emotional upset
+Diagnosis by exclusion: Absence of any other neurologic disease or chronic pain syndromes that could explain stiffness and rigidity
Electrophysiology, EMG:
Continuous motor-unit activity:
- & limbs
- Disappears with IV diazepam, sleep, and local or general anesthesia
- Note: preservation of silent period after muscle contraction
- Abnormal co-contractions of antagonistic muscles
- Intermittent superimposed contractions: Continue into drowsiness & interfere with sleep
- Spasmodic reflex myoclonus
Antibody tests:
- Anti-glutamic acid decarboxylase GAD antibodies, anti-amphiphysin antibodies, anti-Gephyrin antibodies
- Associated with other autoimmune disorders e.g. diabetes, thyroid disease
Treatment:
Symptomatic:
- 1st line: diazepam orally qid
- 2nd line: baclofen
- Others:
- vigabatrin, Valproate VPA, Gabapentin GBP
Disease altering:
- Treat underlying tumor if present
- IVIg
- Steroids
- Plasmaphoresis