There is much to be gained from joint work with interested psychiatric colleagues.
While the title of this article draws attention to the risk of mistaking “neurological” disorders for psychiatric ones, the opposite mistake is almost certainly more common.
Cognitive and behavioural involvement is the rule, not the exception, among patients with disorders of the central nervous system (CNS).
The physical and psychological symptoms of disease can therefore be related in the following ways: (1) physical symptoms come to light by way of complex psychological processes; (2) psychological upset can manifest itself in physical symptoms; (3) physical diseases commonly cause a secondary psychological reaction; (4) one category of physical disease, affecting the brain, can give rise, more or less directly, to psychological manifestations.
Peripheral nerve involvement and motor dysfunction characterise the initial presentation of the infantile and juvenile forms.
In the rarer adult form, cognitive and psychiatric features predominate and patients may present with dementia or psychosis.
Inherited leucodystrophies can present with neuropsychiatric features.
Metachromatic leucodystrophy, for example, caused by a deficiency of the lysosomal enzyme arylsulphatase-A (ASA) leading to demyelination in peripheral and central white matter, has infantile, juvenile, and adult forms.
Neurology has an especially close relationship with psychology and psychiatry, as all three disciplines focus on the functions and disorders of a single organ, the brain.
This is well recognised in some conditions—for example, Huntington’s disease, which is commonly associated with depression, apathy and aggressivity, and sometimes associated with psychosis, obsessive–compulsive disorder and suicide; these features, or the predominantly subcortical dementia of Huntington’s disease, can precede or overshadow the associated chorea.
Wilson’s disease presents with primarily neuropsychiatric symptoms including personality change, mood disturbance, psychosis, and cognitive impairment in around one third of cases.
This is to emphasise that, although brain disorders are often carved up into these subcategories for practical or heuristic purposes, these distinctions are often tenuous.
The cognitive, psychological, and behavioural sequelae of CNS disorders depend, inter alia, on: the tempo of the underlying disorder; the brain regions it affects; the neurotransmitter systems it involves; and various individual characteristics, such as age, sex, and psychosocial background: Many of the inherited disorders of the central nervous system have neuropsychiatric as well as traditionally “neurological” manifestations.
We cannot possibly discuss all the neurological disorders which can be mistaken as psychiatric in this short article: we have picked out an illustrative assortment to convey the broad approach we recommend.