Epidemiology

This is a very common problem. It is estimated that perhaps less than half of all patients attending neurological outpatients in the UK have clinical features which are fully explained by a defined neurological disease or "organic" neurological disorder.

Pathophysiology

By definition the pathophysiology of medically unexplained symptoms is unknown. The term is generally applied to symptoms and signs which the clinician considers are partly or wholly caused psychological factors. Depression or anxiety is very common.

Other descriptive terms which have been used include: hysteria, hypochondriac, somatisation disorder, non-organic, functional.

Clinical Features

The commonest neurological presentation is with weakness, either affecting one side of the body (hemiparesis) or the legs (paraparesis). Sometimes the weakness is confined to one limb (monoparesis) and almost any combination of weakness is possible. The pattern of weakness, and of the limb reflexes, is different from that which would be expected in upper or lower motor neurone nerve damage. Inconsistency of weakness is a useful clinical clue.

Sensory loss or pain are also extremely common and any neurological symptom can be included; again, the main clues are inconsistency and a variation from what is expected on anatomical grounds.

The personal, social and medical background are extremely important and often complex; however detailed information on all these aspects is usually absent at the initial outpatient or hospital attendance. Exclusion of an "organic" neurological cause is the usual priority for both patient and their doctor. Even if the initial tests are normal, there is often concern that "something has been missed".

Investigation

Investigation to exclude neurological disease, which could reasonably explain the symptoms is appropriate. This frequently involves imaging the brain or spine and blood tests. More specialised investigation can be done in selected cases. Investigations should be done once and not repeated unless there are new clinical features.

Management

There cannot be a single strategy for such a diverse group and each case has to be approached individually. Usually psychological issues are addressed once neurological disease has either been excluded or its contribution acknowledged. Referral to a psychiatrist may be useful in some cases. Most cases are managed in primary care, with a multidisciplinary approach.

Prognosis

The risk of harbouring an undiagnosed neurological disease, undetected after initial investigation, is low at about 5%. In many cases, symptoms settle quickly with reassurance. However if symptoms persist for over a year, the chances of recovery are small.

References and Links

Rew DA, Wilson GD. Medically unexplained physical symptoms. Do not overinvestigate. BMJ 1991; 303: 534-5.

Crimlisk HL et al. Slater revisited: 6 year follow up study of patients with medically unexplained symptoms. BMJ 1998; 316: 582-6.

Carson AJ et al. Do medically unexplained symptoms matter? A prospective cohort study of 300 new referrals to neurology outpatient clinics. J Neurol Neurosurg Psychiatry 2000; 68: 207-10.

By Dr Will Honan FRCP