I’ve just found this fascinating case study in American Journal of Physical Medicine and Rehabilitation about a man who lost conscious control over one of his hands after brain injury and suffered involuntary public masturbation episodes as a result.

Involuntary masturbation as a manifestation of stroke-related alien hand syndrome

Ong Hai BG, Odderson

Am J Phys Med Rehabil. 2000 Jul-Aug;79(4):395-8.

Alien hand syndrome is a perplexing and uncommon clinical diagnosis. We report an unusual manifestation of alien hand syndrome in a 73-yr-old man with a right anterior cerebral artery infarct affecting the right medial frontal cortex and the anterior portion of the corpus callosum. We conclude that alien hand syndrome should be considered in patients who present with a feeling of alienation of one or both upper limbs accompanied by complex purposeful involuntary movement.

We tend to think of the cognitive impairments after brain injury as the most disabling – things like loss of memory or speech or language impairment, but we often neglect what we might call social impairments.

Especially when the effect is embarrassing, these can have just as strong an impact because many people massively restrict their lives to prevent causing social discomfort to themselves or others.

Link to PubMed entry for study.