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Source: Askmark H, et al. Parkinsonism and neck extensor myopathy: A new syndrome or coincidental findings? Arch Neurol. 2001;58:232-237.
Among 459 patients evaluated for parkinsonism between January 1997 and December 1999, 7 were found to have a dropped head with neck extensor weakness on examination. All 7 demonstrated dysautonomia and 6 did not respond to levodopa, consistent with a diagnosis of multisystem atrophy. Parkinsonism was the initial symptom in 5, head drop in 2. Five were found to have mild, moderate (n = 1 each), or profound (n = 3) neck rigidity. All 7 showed myopathic changes on needle electromyography of paraspinal or neck muscles (splenius, scalenus, semispinalis, trapezius) and muscle biopsy. The latter, performed in 5, showed noninflammatory myopathy, with mitochondrial abnormalities on electron microscopy in 2. Neck extensor weakness and a droopy head in parkinsonism may be caused by a primary myopathy and should raise the diagnostic possibility of multisystem atrophy.
Dropped head syndrome is an affliction of mixed etiology, resulting from disease anywhere along the motor unit, and beyond. Inflammatory myositis (polymyositis, dermatomyositis, inclusion body myositis), noninflammatory myopathy with or without necrosis, unspecified congenital myopathy, adult-onset nemaline myopathy, and muscular dystrophy (facioscapulohumeral dystrophy) may cause predominant weakness of neck extensors (J Clin Neurosci. 2000:7;334-336; Neurology. 1992;42;1625-1627; J Child Neurol. 1994;9;330-331; Muscle Nerve. 1999;22;115-118; Ann Neurol. 1986;20:133). Neuromuscular transmission defects (myasthenia gravis), neuropathy (chronic inflammatory demyelinating polyneuropathy), and anterior horn cell disease (amyotrophic lateral sclerosis) are also causative (Ann Neurol. 1986;20:133); Muscle Nerve. 1994;17:808-810). Hypokalemia, in addition to causing a vacuolar myopathy, may result in relatively acute neck muscle weakness (Neurology. 1993;43:846-847), and either hypothyroidism or hyperparathyroidism may cause a slowly progressive, severe dropped head (Neurology. 2000;55:896-897; Rev Rhum Ed Fr. 1993;60:467-469). Malignancy, postpolio syndrome, mitochondrial myopathy, and Cushing’s syndrome are other associations (Muscle Nerve. 1999;22:115-118). Some remain cryptogenic. Serum creatine kinase is usually normal, though levels up to 4800 U/L are reported in secondary cases (Neurology. 2000;55:896-897). Needle electromyography of cervical paraspinal muscles shows low amplitude, short duration, polyphasic (myopathic) motor unit potentials with fibrillation potentials, and muscle biopsy in primary cases. These usually reveal nonspecific myopathy without evidence of inflammation. Treatment of an underlying condition, where present, is beneficial. Sometimes in cryptogenic cases, isolated instances of improvement have been reported following immunosuppression with azathioprine and prednisone (Muscle Nerve. 1999;22:115-118) or intensive physiotherapy (Disabil Rehabil. 1999;21:563-565). —Michael Rubin
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