Functional disorders are one of the most common reasons for attendance at the neurology clinic. These disorders — at other times and in other places called psychogenic, non-organic, conversion, or hysterical — encompass symptoms such as paralysis, tremor and other abnormal movements, gait disorders, and seizures. The term functional disorder refers to a genuinely experienced symptom which is often disabling and distressing but which relates to abnormal nervous system functioning, rather than a conventional disease process such as epilepsy or multiple sclerosis (Figure 1). Modern treatment involves making a clear diagnosis, educating patients about the disorder, and sometimes offering cognitive behavioural therapy or physiotherapy. But despite growing interest and awareness of these disorders, our treatments are often not effective and many patients have longstanding disability requiring, for example the use of a wheelchair.

In recent years, small trials of treatments using transcranial magnetic stimulation (TMS) and other forms of electrical stimulation have produced very promising results. TMS, and its cousin TDCS is also being used in conditions like migraine and even as a cognitive enhancer. A commercial market has appeared for these devices. This looks at first sight like a surprising new turn. Yet, little is as new as it looks; electricity has been used medically since the 18th century, and has been used to treat functional disorders — identified, anachronistically, in our review of historical medical case reports, treatises, and textbooks — from the moment devices were capable of delivering a ‘shock’.

The Leyden Jar (Figure 2, Figure 3) was invented in 1745-6: a portable device for storing and discharging sparks. The earliest descriptions of medical use of the Leyden Jar include reports of sudden cures of weakness and contractures which are highly suggestive of modern functional disorders.

Cleric John Wesley, in his 1759 Desideratum: Or Electricity made Plain and Useful by a Lover of Mankind and of Common Sense describes treating a 22-year-old woman with likely dissociative (non-epileptic) seizures (part of the spectrum of functional disorders) using the ‘ethereal fire’ of electricity: ‘On the first Shock her struggling ceased, and she lay still. At the Second her Senses returned. After two or three more, she rose in good Health.’ Similarly Benjamin Franklin, in 1754, successfully treated a 24-year-old woman with multiple ‘hysterical’ symptoms including ‘cramps in different parts of the body’ and ‘general convulsions of the extremities.’

By the mid 19th century many large hospitals had electrical departments with Leyden jars, batteries (developed by Galvani and Volta between 1791 and 1800), and after Faraday’s discovery in 1831, electromagnetic induction machines. Some advocated localized faradization, applying electrical current to the functionally weak body part. Others, believing hysteria to be a constitutional disorder, recommended general faradization (Figure 3) to the body as a whole.

At the turn of the 20th century, Charcot, Babinski, and Freud used static baths, sparks and faradization in the diagnosis and treatment of hysterical symptoms, although Freud later rejected electrotherapy stating (in An Autobiographical Study) that any good results were entirely the result of suggestion.

In contrast, Lewis Yealland, who described extensive use of electrical therapy in shell-shocked soldiers in his 1918 Hysterical Disorders of Warfare, believed that electricity worked purely by suggestion and was no less effective or valuable for this reason. Some of Yealland’s methods now seem cruel: the application of electricity to the tongue in soldiers with hysterical aphonia, so vividly portrayed in Pat Barker’s novel Regeneration and in the film adaptation of the same. Its reputation tainted, reports of electrotherapy diminish after World War I as psychotherapy gained ground as the treatment of choice.

All was then quiet, until the most recent wave of electrical treatments for functional disorders. The first ‘new’ treatment, Transcutaneous Electrical Nerve Stimulation (TENS), developed during the 1970s and a refined form of early cutaneous faradization, has been trialed with some promise in an uncontrolled series of 19 patients with functional movement disorders.

Transcranial Magnetic Stimulation (TMS) (Figure 4) differs from peripheral TENS by delivering a magnetic burst rather than electrical shock and targeting the motor cortex of the brain rather than the motor nerve of an affected limb. But the effect is somehow similar: a shock-like sensation and sudden involuntary movement. The first case report of a patient with functional symptoms improving with TMS was published in 1992, and several subsequent studies have investigated TMS as a treatment, one study describing success in 89% of 70 patients and another 75% of 24 patients.

Authors of these modern studies tend not to reference older electrical treatments. Yet, not only has the treatment been around for a long time, but so have the various ideas about how it works. Modern TMS researchers acknowledge some role for suggestion or placebo but also speculate about changes in the brain, for example suggesting “rTMS may have the ability to restore an appropriate cerebral connectivity by activating a suppressed motor cortex.”

In our article published in Brain we argue that TMS in functional disorders is the latest expression of a repeating cycle of electrical experimentation — first with Leyden Jars, then early batteries, then electromagnetic apparatus — recurring since the mid-18th century. Doctors first attribute improvement, or cure, to powerful biological or even metaphysical effects. With time and experience these explanations are replaced with a view that the treatment works by suggestion, placebo, or by demonstrating the possibility of improvement. This does not rest well with many practitioners, and the treatment is set aside. We suspect that emerging technology such as transcranial direct current stimulation will follow a similar pattern.

Difficulties remain. If these treatments do work through suggestion, modifying expectation or perhaps just demonstrating the potential for recovery is that necessarily a bad thing if they ultimately help the patient? Is there a way we can use the treatments explicitly with patients explaining all of this while keeping the efficacy of the treatment? Discomfort with these questions has in the past discouraged ongoing use of electrical treatments, even when they really seem to have helped. A recently-proposed paradigm of the basis of functional disorder suggest that high order beliefs can influence sensorimotor processing at a neuronal level. Distinctions between what a biological and psychological mechanism are at last starting to break down.

Perhaps we do not need to discard these treatments, which after all have repeatedly been shown to help patients. Maybe by confronting transparently, with patients, the uncertainties regarding mechanism of action we can continue to use these treatments as part of our armoury of techniques to help individuals with functional disorders.

Featured image: Apparatus for applying an electric shock. Showing Leyden jar, Lane’s electrometer and ‘directors’ or conductors. Wellcome Library, London. CC BY 4.0 via Wellcome Images.