Second edition

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76 Abnormal movements
Table 3.2 Causes of myoclonus
Associated with delirium
Serotonin syndrome (Feighner et al. 1990; Sternbach 1991)
Hashimoto’s encephalopathy (Castillo et al. 2006; Ghika-Schmid
et al. 1996)
Uremic encephalopathy (Mahoney and Arieff 1982)
Hyperosmolar non-ketotic hyperglycemia (Morres and Dire 1989)
Encephalopathic pellagra (Serdaru et al. 1988)
Baclofen withdrawal (Meythaler et al. 2003)
Arbovirus encephalitis (Kleinschmidt-DeMasters et al. 2004)
Encephalitis lethargica (Blunt et al. 1997; Walsh 1920)
Complex partial status epilepticus (Kaplan 1996)
Bismuth intoxication (Supino-Viterbo et al. 1977)
Leaded gasoline intoxication (Goldings and Stewart 1982)
Bromide intoxication (Obeso et al. 1986)
Mercury intoxication (Roullet et al. 1994)
Associated with dementing disorders
Creutzfeldt–Jakob disease (Brown et al. 1986)
Post-anoxic encephalopathy (Werharhan et al. 1997)
Subacute sclerosing panencephalitis (both child [Dawson 1934]
and adult [Prashanth et al. 2006] onset)
Diffuse Lewy body disease (Louis et al. 1997)
Corticobasal ganglionic degeneration (Rinne et al. 1994)
Multiple system atrophy (both striatonigral [Wenning et al. 1995]
and olivopontocerebellar variants [Rodriguez et al. 1994])
Progressive supranuclear palsy (Collins et al. 1995)
Huntington’s disease (both adult [Salt et al. 2006] and juvenile
[Siesling et al. 1997] onset)
Alzheimer’s disease (Benesch et al. 1993; Chen et al. 1991)
Dentatorubropallidoluysian atrophy (Becher et al. 1997)
Acquired immune deficiency syndrome (AIDS) dementia
(Maher et al. 1997; Navin et al. 1986)
Dialysis dementia (Chokroverty et al. 1976; Garrett et al. 1988;
Lederman and Henry 1978)
Epilepsies
Juvenile myoclonic epilepsy (Jain et al. 1998; Panayiotopoulos
et al. 1994; Pedersen and Petersen 1998)
SSRI selective serotonin reuptake inhibitor.
dyskinesia subtypes, occurs only after long exposure to
antipsychotics; although tardive myoclonus may appear in
isolation, it is often accompanied by tardive dystonia.
Regarding the miscellaneous causes of myoclonus, several
comments are in order. As noted earlier, myoclonus is characteristic
of post-anoxic dementia; however, an episode of
anoxia may be followed by myoclonus alone and in such
cases the term ‘Lance–Adams syndrome’ is used, in honor of
Lance and Adams who first described it in 1963. Lesions, for
example infarction of the frontoparietal cortex or the thalamus,
may cause myoclonus and months or longer may elapse
between the infarct and the appearance of the abnormal
movement. Lesions of the spinal cord, such as infarction,
myelitis or trauma, may cause myoclonus, which may be
either focal, reflecting the segment involved, or generalized:
this generalized form, often referred to as propriospinal
Unverricht–Lundborg disease (Koskiniemi et al. 1974;
Magaudda et al. 2006)
Myoclonic epilepsy with ragged red fibers (Berkovic et al.
1989)
Lafora body disease (Yokoi et al. 1968)
Kufs’ disease (Berkovic et al. 1988; Nijssen et al. 2002)
Medications
Gabapentin (Zhang et al. 2005)
Lamotrigine (Crespel et al. 2005)
Meperidine (Kaiko et al. 1983)
Hydromorphone (Hofmann et al. 2006)
SSRIs (Barucha and Sethi 1996)
Tricyclic antidepressants (Casas et al. 1987; DeCastro 1985;
Garvey and Tollefson 1987; Lippmann et al. 1977)
Trazodone (Garvey and Tollefson 1987; Patel et al. 1988)
Lithium (Caviness and Evidente 2003)
Buspirone (Ritchie et al. 1988)
Clozapine (Bak et al. 1995; Barak et al. 1996)
Levodopa (Klawans et al. 1975)
Amantadine (Matsunaga et al. 2001)
Trimethoprim/sulfamethoxazole (Dib et al. 2004)
Tardive myoclonus (Abad and Ovsiew 1993; Little and Jankovic
1987; Wojick et al. 1991)
Miscellaneous causes
Lance–Adams syndrome of post-anoxic action myoclonus
(Lance and Adams 1963)
Infarction of the frontoparietal cortex (Sutton and Meyere
1974) or thalamus (Kim 2001; Lehericy et al. 2001)
Spinal cord lesions (De La Sayette et al. 1996; Hoehn and
Cherrington 1977; Keswani et al. 2002)
Paraneoplastic myoclonus (Bataller et al. 2001)
Whipple’s disease (Louis et al. 1996)
Celiac disease (Tison et al. 1989)
Myoclonus dystonia (‘essential myoclonus’ [Mahloudji and
Pikielny 1967])
myoclonus, typically affects the trunk and extremities.
Paraneoplastic myoclonus reflects autoimmune involvement
of the brainstem and is often accompanied by opsoclonus
(Digre 1986). Rare causes of myolonus include Whipple’s
disease and celiac disease. Finally, myoclonus may also
occur on an inherited basis, namely as the syndrome of
myoclonus–dystonia (Asmus et al. 2002; Doheny et al. 2002;
Foncke et al. 2006; Grimes et al. 2002; Schule et al. 2004). This
syndrome, also known as ‘essential myoclonus’, is inherited
on an autosomal dominant basis with incomplete penetrance.
Onset is in childhood or adolescence, and, in addition
to myoclonus there may also be cervical or task-specific dystonia
(e.g., writer’s cramp). Of interest, there appears to be
an association between myoclonus–dystonia and obsessive–
compulsive disorder and alcoholism (Hess et al. 2007;
Saunders-Pullman et al. 2002).