Neurology and psychiatry

A primary psychiatric diagnosis is present in 13–27% of new neurology outpatients and evidence of psychiatric morbidity in up to 48%.

Introduction

A psychiatric dimension is common in neurological consultations. Neurological and psychiatric illness may be related in several ways:

Neurological diseases may have psychiatric complications.

Neurological diseases may present with psychiatric symptoms.

Psychiatric illness may present with neurological symptoms. Examples are depression presenting as pseudodementia (p. 55) and non-organic neurological illness (p. 116).

The treatments for psychiatric illnesses can cause neurological complications and vice versa. Drugs of abuse also have neurological and psychiatric complications.

Psychiatric factors may be important in triggering physical diseases, especially those to which the individual has a predisposition, e.g. epileptic seizures or migraine.

Psychiatric complications of neurological disease

Psychiatric complications of neurological disease may be reactive – a response to the handicap of the disease – or a primary manifestation of the disease itself. In some cases, both mechanisms may be active.

Anxiety

Anxiety is a common occurrence in neurology outpatients, found in 25–35%.

Depression

Depression is a common complication, and occurs especially frequently in certain diseases: Parkinson’s disease 50%, Alzheimer’s disease 30%, multiple sclerosis 25%, epilepsy 38%, stroke 25% and following head injury 25%. Depression leads to suicide in 6% of patients with Huntington’s disease, and in epilepsy the suicide risk is 5–25 times that of the general population.

Obsessive-compulsive disorder

This is also seen in movement, especially Parkinson’s disease and Huntington’s disease.

Euphoria

Euphoria, much vaunted, occurs in only 3% of patients with multiple sclerosis. Emotional lability may also be seen as part of pseudobulbar palsy, usually in multiple sclerosis, cerebrovascular disease or motor neurone disease. Pathological laughter or crying (the act without the underlying emotion) may also occur and usually relates to thalamic or brain stem disease.

Delusions

Delusions and other psychotic symptoms are seen in patients with Alzheimer’s disease, vascular dementia, focal epilepsy, multiple sclerosis, treated Parkinson’s disease and post-traumatic brain injury.

Complications of epilepsy

Epilepsy is associated with three patterns of psychotic disorder, best defined by the timing of psychotic symptoms in relation to epileptic seizures. They usually occur in patients with focal epilepsy syndromes and with known epilepsy, but occasionally may be a first presentation:

1. Postictal psychosis. Florid psychotic symptoms follow on from a flurry of severe seizures with a consistent time interval, usually 1–7 days. The episode is usually self-limiting within a week, but may require antipsychotic treatment during that time.

2. Ictal psychosis. Psychotic symptoms occur during the epileptic activity itself, usually as a manifestation of non-convulsive status epilepticus, and there is evidence of altered awareness. Patients may be agitated and hit out, but directed aggression is exceptionally rare. In both these situations, the best treatment of psychosis is to prevent seizures with antiepileptic therapy.

3. Interictal psychosis. Timing bears no relationship to identifiable epileptic seizures. Occurs more often in those with structural lesions (23%) than in mesial temporal sclerosis (5%) and is occasionally caused by antiepileptic drug therapy.

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