The metaphorical barn door applies to the diagnosis of parkinsonism by practising neurologists, and most of these patients have Parkinson’s disease. But the minority have another cause and this may lead to bad loss of face by the neurologist, as I have myself experienced. And on occasion the potent current medical and surgical anti-parkinsonian treatments may prove very mistaken.

My first exposure to “not Parkinson’s disease” were the survivors of the encephalitis lethargica epidemics of the first decades of the 20th century, seen in London in the 1950s and 1960s. The patients differed from those with Parkinson’s disease in having static rather than progressive disabilities, with predominant akinesia, autonomic disorders, and oculogyric crises. One often aggravated their distress by overenthusiastic use of anti-cholinergic drugs. The advent of L-dopa, as related dramatically to the lay public in 1973 by Oliver Sacks in his best-seller Awakenings, brought relief. Then, and since, a rare but perennial problem of not Parkinson’s disease was the medicolegal conundrum of post-traumatic parkinsonsism; the problem lay not in diagnosis or management, but in attributability where the lawyers’ balance of probabilities was bound to err.

In the 1950s a new manifestation of “not Parkinson’s disease” emerged with the successful use of psychotropic drugs such as the phenothiazines. This drug-induced parkinsonism often had dystonic features. The patients were easily spotted by taking a proper drug history, and would remit on withdrawal of the drug. But I recall one humiliating case in whom I started L-dopa treatment. I had failed, for bad reasons, to take a drug history. A less happy outcome resulted when a man whose hypokinesia from inadequately treated hypothyroidism was misdiagnosed as parkinsonian by an eminent neurologist; the small dose of thyroxine was stopped, and he lapsed into “myxoedema coma”, with a stroke, from which he only partly recovered.

A more common mistake, made mostly by non-specialists, is the attribution of familial or essential tremor to Parkinson’s disease in which, of course, the rest tremor is lessened by action. But I have known one instance where this was done by an experienced neurologist who worsened the patient by medical and surgical anti-parkinsonian treatments. The concept of progressive and severe disability from essential tremor was introduced into the English neurological literature by Macdonald Critchley in the late 1940s and promoted by his nephew Edmund Critchley, who discussed associated neurological disorders in advanced cases.1 It is not helped by anti-parkinsonian drugs; many patients are less tremulous if they take alcohol—which brings obvious new problems.

A depressing, and perhaps increasingly common group of conditions which are not Parkinson’s disease are what Barbeau termed “Parkinsonism Plus”.2 While the majority of sufferers from Parkinson’s disease remain intellectually intact, and deserve reassurance, a minority do dement from Lewy body or Alzheimer’s disease, which may or may not be part of the same pathological process. In a very few there may be graver problems with failure of vertical eye movements (progressive supranuclear palsy) or significant autonomic failure (Shy-Drager syndrome, multiple system atrophy)—all progressive and intractable.

More challengingly and less depressingly, there are a few in the very large population of dements with mobility problems (elderly, mostly) who have treatable hydrocephalus as the cause. This may be a consequence of past brain trauma, meningitis or subarachnoid haemorrhage, or it may be idiopathic—a failure of Harvey Cushing’s “third” (CSF) circulation.3 This syndrome was first described by Salomon Hakim in Bogota in 1964, and published from Boston where he had trained in 1965;4 its three main features are dementia, incontinence and a gait disorder, with response to CSF tapping and drainage by a shunt into the atrium or peritoneum. Referrals from Edinburgh physicians, psychiatrists and geriatricians enabled me to jump on this bandwagon in the early years, and I was delighted with some excellent results from CSF shunting, most of my later cases operated on by Mr James Steers. Analysing my first 15 cases, I was intrigued by the great variability of the length of the history—weeks, years or even decades—often with fluctuations of the severity. The gait disorder was often bizarre, with good power and coordination of the legs when tested on the bed but inability to walk—that is, an apraxia of gait, mimicking a functional disorder.

In retrospect one of the 15 should not have been shunted: a young woman who probably had hydrocephalus from childhood meningitis, and whose later Wilson’s disease failed to respond to penicillamine; she died. Nine out of the 14 survivors seemed to benefit, five to the extent of becoming normal, and remaining so. The partial successes included two who became continent and walked much better, but failed to make a complete intellectual recovery, although the size of their ventricles had returned to normal. Two of the failures who came to postmortem had blocked shunts, one by a clot at the atrial end of the shunt, the other by peritoneal fibrosis around the peritoneal end of the theco-peritoneal tubing. Other serious complications were shunt infection in one, treated successfully, and subdural haematomas in another, with lasting damage. More recent larger series, despite better follow-up and more sophisticated shunt valves, still record comparable complication rates: 24% of Malm and Eklund’s 147 cases required shunt revision with eventual improvement in 70% to 80%;5 and 33% of Williams’ 132 cases required shunt revision, with some improvement in 75%.6

My own later experience of hydrocephalus was changed by more widespread diagnosis thanks to the greater availability of brain scanning to non-neurologists, and the popularity of the paradoxical label “normal pressure hydrocephalus”, resulting in more direct referrals to the surgeons. In fact, the CSF pressures are not normal, as appreciated by the original authors who had “normal” in inverted commas in their title. Of course cases continued to come my way after the first 15. A very humiliating one was a lady I had diagnosed with Parkinson’s disease, and she improved with L-DOPA. Three years later she became incontinent. Fortunately, despite the delay, she responded to Mr Steers’ shunting, and became normal, even after stopping L-DOPA. Thus, what had looked like straightforward Parkinson’s disease to a neurologist (with a particular interest) proved to be the presenting symptom of hydrocephalus, and I have seen one other with a similar presentation.

Adult hydrocephalus is a curable disorder, but CSF shunting still has an appreciable complication and failure rate.5, 6 It needs meticulous and expert follow-up.7 Nonetheless I would find it difficult to justify inclusion of a patient who satisfies clinical and radiological diagnostic criteria (that is, disproportionate ventricular dilatation with little cortical atrophy) in a randomised trial of shunting versus non-shunting, as proposed in a recent Cochrane review which mentions such trials in progress on both sides of the Atlantic.8

ABOUT THE AUTHOR

Dr Jellinek was a consultant neurologist in Edinburgh from 1966 to 1987 when he retired from the National Health Service. He continued to see patients privately until 2003.