Stiff-Person Syndrome Presenting with Headache

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Stiff-person (or stiff-man) syndrome (SPS) is a rare neuromuscular disorder characterized by axial and limb muscle rigidity and spasm. Painful spasms of muscle can be provoked by sudden noise, strong emotional or other startle stimuli. Electrophysiological studies show continuous low-frequency firing of motor units and simultaneous activity in agonist and antagonist muscles of the affected region that can be abolished by central or peripherally acting agents or neuromuscular blockade (1). An autoimmune basis for the disorder is postulated, based on the presence of antibodies against glutamic acid decarboxylase (GAD) found in 90% of cases defined by strict criteria (2). GAD is the rate-limiting enzyme involved in the synthesis of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter. Many affected patients have other autoimmune disorders such as pernicious anaemia, vitiligo and thyroid malfunctions (3). A reduction in brain levels of GABA has been demonstrated on magnetic resonance (MR) spectroscopy scans (3). The loss of inhibitory input from spinal interneurons is theorized to lead to an impaired balance between inhibitory and excitatory influences on muscle activity (4). SPS usually begins insidiously with persistent aching and stiffening of axial muscles. Involvement of the face, neck, abdomen and arms is less typical. Headache as a presenting or major feature of the illness has not been described. Examination generally shows global muscle stiffness, with no other neurological abnormalities, and no abnormalities on computed tomography (CT) or MR imaging of the brain. Treatment is based on enhancing inhibitory activity in the spinal cord through the use of drugs such as diazepam, baclofen and vigabitrin that boost GABA neurotransmission. Steroids, plasmapheresis and intravenous immunoglobulin are also helpful (3). There are reports of improvement in severe muscle spasms and dystonia with the use of botulinum toxin (5). The authors report the case of a 34-year-old male with SPS in whom headache was the presenting feature, and a complicating feature throughout the illness.