In The Field

AAN: Historical highlights – Henry Head


Close observation of the conference program reveals that there’s more to the AAN meeting than quickfire slide presentations on the efficacy profile of PYM50028 for parkinsonism, or discussions of onabotulinumtoxinA for chronic migraine (more on that later). Yesterday I indulged my fascination with history and swung by an afternoon session on Landmark Cases in Neurology.

This kind of thing turns out to be a hobby for neurologists who obviously can’t get enough neuro during any given day in the lab or clinic. Michael Okun, a specialist in deep brain stimulation at the University of Florida, gave a presentation on the British physiologist Henry Head, a project he has been working on in conjunction with some of his neurology students.

Head completed his degree at Cambridge University in 1890, and went on to study the sensory nervous system, becoming interested in how people perceive sensation. He made several important (and still relevant) contributions to our understanding of nerves in the body (the peripheral nervous system), for example pinpointing the involvement of nerves in shingles.

One thing that frustrated him intensely was the fact that when he asked patients about the sensations they could perceive, for example after an injury, they were simply not precise enough for his exacting scientific purposes. So he took radical action.

He decided to experiment on himself. For months he taught himself how to objectify, as far as possible, his responses to stimulation and sensation on his skin, and then in April 1903, he had his friend, a surgeon by the name of Sherren, sever the branches of the radial nerve in his left forearm. Over the month and years that followed, he documented the different types of sensation as they were first abolished and then gradually returned to his arm. On the basis of these experiments, two things emerged: one, Head and Sherren devised a theory dividing the actions of nerves into two types: protopathic, the primitive pain-recognising system, which recovered first, and epicritic, which discriminated fine touch and painless stimuli. It’s questionable whether this division is still useful today. Two, Head discovered to his chagrin that sensory testing was still flawed.

It would be fair to say that Head’s contributions to understanding the nervous system have not been well-received in all quarters – some critics have said he actually hindered the development of knowledge in his field – but his career, and his self-experiment, emphasised the shortcomings of the sensory exam and the difficulties of its interpretation. Worth severing your left arm for? I’ll let you decide…


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