Somatic hallucinations may be described as bodily senses stimulated by the perception of a physical experience occurring within the body.
Simply defined somatic hallucinations are hallucinations of bodily sensation affecting the skin, muscle and joint sense and inner organs, and can include sensations of heat or cold, electric shocks, sexual experiences and visceral sensations.
Bodily sensations or somatic hallucinations may fall into one of the categories of superficial, kinesthetic, or visceral. We'll spend the remainder of this literature discussing these categories.
Superficial hallucinations
Superficial hallucinations affecting skin sensation may be either one of the following subtypes:
Thermal (or themic) — A false perception of heat or cold (e.g., ‘my feet on fire’).
Tactilehallucinations — The term tactile hallucination is used commonly to describe hallucinations Opens in new window affecting the skin, e.g., the experience of the skin being touched (‘a dead had touched me’), pricked or pinched.
Tactile hallucinations are unique, in that they are invariably delusionally elaborated; the commonest delusions are those of being controlled. This is somatic passivity, which is a first rank symptom.
Haptic hallucinations — Haptic hallucinations may be experienced as touch (‘like a hand stroking me’) or painful (‘knives stabbing my neck’). A patient believed that the smoke sensor in the ward was an infrared camera, ‘because I feel it warm on my neck’.
Another patient described a haptic hallucination in which she experienced genital stimulation that she ascribed to having sexual intercourse simultaneously with ‘both Kennedy brothers all the time’. It is important to realize that there is both a hallucinatory Opens in new window and a delusional Opens in new window component in such experiences.
One particularly unpleasant form of haptic hallucination is called formication (Latn: formica, ‘ant’), the unpleasant of little animals or insects crawling over the body or just under the skin. This is especially associated with some drug states and withdrawal symptoms, for example cocaine addiction and alcohol withdrawal. It is often associated with delusions of infestation, but the latter may occur without hallucination.
Hygric — is a false perception of a fluid, e.g. ‘All my blood has dropped into my legs and I can feel water sloshing in my brain’.
Paresthesia — is the term describing the sensation of tingling or ‘pins and needles’. These may be delusionally ascribed, although of course they are often neurologically mediated, for example ulnar nerve compression causing pins and needles in the forearm.
Kinesthetic hallucinations
Kinesthetic hallucinations are those of muscle or joint sense. The patient feels that his/her limbs are being bent or twisted; or in some cases the muscles may exhibit a sensation of being squeezed.
Such hallucinations in schizophrenia Opens in new window are often linked with bizarre somatic delusions. A man suffering from schizophrenia described the experience thus: ‘I thought my life was outside my feet and made them vibrate’ — he experienced kinesthetic hallucinations of vibration.
Kinesthetic hallucinations may occur in organic states: ‘a feeling of being rocked about’. Abnormal kinesthetic perceptions have also been observed in the withdrawal state from benzodiazepine drugs (Schopf, 1983) or from alcohol intoxication. A man, after recovery, described his episode of delirium tremens, saying, ‘I felt as if I was floating in the air about fifty feet above the ground’.
Visceral hallucinations
Visceral hallucinations are false perceptions of the inner organs. Patients may be distressed by deep sensations of their organs throbbing, stretching, distending or vibrating.
There is only a limited range of possible visceral sensation, for example pain, heaviness, stretching or distension, palpitation and various combinations of these, such as throbbing.
However, the possible range of bizarre schizophrenic false perceptions and interpretations is limitless. One man believed that he could feel semen travelling up his vertebral column into his brain, where it became laid out in sheets.
Hallucinations of bodily sensation are quite common in schizophrenia and are almost always delusionally elaborated, often delusions of control.
