03 November 2005

Self-injurious behavior

A number of cases have been reported in which patients are said to have damaged or destroyed areas of body afflicted by neuropathic pain and sensory deficit (the latter being an inevitable accompaniment of the former) (see Mailis, 1996).

In 30 years of pain clinic practice with a particular emphasis on neuropathic pain, I have seen two only patients in whom ‘self-injurious behaviour’ (Mailis, 1996) has occurred. Patient 1 was one of 160 patients with central post-stroke pain (CPSP) personally seen and examined by myself; Patient 2 was one of 282 patients with postherpetic neuralgia (PHN) personally seen and examined by myself.

Patient 1 was a right-handed man who had a stroke at age 66 affecting the left side of his body, including the face. He was aphasic, and remained so for 6 weeks; he had hiccoughs which persisted for 2 or 3 months. There was severe loss of power in his left arm and leg.

Burning and shooting pain appeared in the left side of his face some 3 months later.

He was first seen in the Pain Clinic 2 years after the stroke. By this time his motor deficit was almost imperceptible. He still complained of burning and shooting pains in the left side of the face, particularly at the tip of his nose; he also had occasional pins and needles in his left arm and even less frequently in his left leg. He stated that his facial pain was exacerbated by drinking hot liquids; that the left side of his face always felt hot, and sometimes went red for 3 or 4 weeks at a time. On examination, tactile and sharpness sensations were diminished on the left side of the face, particularly on the outer lower left side of his nose, and to a lesser extent in his left arm. There was no clinically evident deficit of temperature sensation.

The ala nasae of the left nostril was absent, leaving a half-moon-shaped gap extending about 7.5 mm up the nose in comparison with the right side. He said that he had ‘picked and pulled’ at his nostril ever since the pain came on, because that was where the pain was worst. His GP confirmed that this self-inflicted mutilation had occurred since the central post-stroke pain came on. The patient averred that he still felt pain in the ‘missing part’ of his nose.

He had had a stellate ganglion block and an intravenous infusion of lignocaine in another hospital before being referred to us; neither had had any effect on his pain. We prescribed nortriptyline, rising to 75 mg nocte. This also had no effect, and the patient discharged himself after 3 months.

Patient 2 was an apparently phlegmatic male farmer born in 1912 who had herpes zoster affecting his right ophthalmic nerve (V1) in 1984, at the age of 72. When seen in the Pain Clinic 2 years later, aged 74, he had some mild backache but was otherwise an extremely healthy man, still working. He complained of a pain on the right side of his forehead which he described on his McGill Questionnaire as "Throbbing, boring, pressing, pulling, and hot". He had some mild dynamic tactile allodynia. Amitriptyline, rising to 50 mg nocte, was prescribed. When next seen in a follow-up clinic, a few months later, he stated that he felt ‘much better’. However, the following year he had a mild stroke, which resulted in him being treated with Madopar® 62.5 mg b.d.

He was next seen in the Pain Clinic 9 months later (now aged 75). There were no evident symptoms or signs of stroke; he was then taking a proprietary drug containing both an anticholinergic and a calcium channel blocker. His forehead pain was still described as ‘much better’.

Beginning 3 months later, he complained that he ‘couldn't feel the right side of his forehead’. He had begun to scratch the area, resulting in red scratchmarks. When asked why he did this, he denied that there was any pain or itching, but said that as he couldn't feel anything, he wanted ‘to make sure it was still there’. Clinical testing confirmed the absence of tactile and sharpness sensations, and severe diminution of temperature sensation; an area about 3 cm wide and 4 cm wide centred above the middle of the right eyebrow could be said to be virtually anaesthetic.

He was seen at frequent intervals over the next 4 years. Within 18 months, he had scratched his forehead down to the bone in circular area of about 1.5 cm diameter about 2.5 cm above the middle of the right eyebrow, surrounded by a rectangular area in which injury changed centripetally from down to periosteum to more superficial cutaneous layers. He prevented the process of healing by repeated scratching. He repeatedly denied that he felt any pain, but said that there was some ‘irritation’. As he was clean-shaven, he was asked whether or not he didn't think that seeing his forehead in a shaving mirror every morning confirmed that it was indeed present. He admitted this, but said it had become a habit during the day to touch and subsequently scratch, harder and harder, to see if he could elicit any sensation which would confirm its presence. Medical treatment with both external applications of benzydamine and lignocaine creams, and systemically with tricyclics, carbamazepine, baclofen, and buprenorphine had no effect; neither did transcutaneous nerve stimulation, stellate ganglion or supraorbital nerve blocks.

Neither of our patients was assessed by a clinical psychologist. However, both appeared to be of normal intelligence; both were married men doing responsible jobs. They may well have been exogenously depressed by their illness, but showed no obvious clinical signs of endogenous depression at interview. They thus did not overtly exhibit two of the criteria listed by Mailis (1996) for self-injurious behaviour (SIB): low intelligence and depressive personality.

Many of the cases of SIB reported in the literature (which has been extensively reviewed by Mailis, 1996) were of ‘ulcers’ and ‘excoriations’. Injury of this sort is undoubtedly under-reported. However, both the cases reported here had extensive and unequivocal injuries. It is interesting, and perhaps significant, that both involve the face, for by far the greatest number of reported self-inflicted injuries are facial, in patients with anaesthesia dolorosa following destructive procedures of the trigeminal ganglion.

Prima facie, it would seem that the first patient reported herein was a genuine case of autotomy; he destroyed a painful part, in which he subsequently continued to have phantom pain.

The second patient, however, mutilated an area from which he had no apparent sensory input. This is an extreme case of a much commoner clinical phenomenon: following peripheral nerve injury resulting in an anaesthetic area of skin, most patients take no notice of it, except to remark, if directly questioned, that they have an area in which there is no feeling. A small number, however, become obsessed with a perfectly painless but anaesthetic area. The patient reported here is such a case, although the only one in our experience who has injured himself as a result.

However, another case involving a patient with HZ-PHN has been reported to me anecdotally by Dr R.W. Johnson (Bristol). This concerns an elderly man who had facial zoster, and subsequently had violent itching in his analgesic right ala nasae. Because he could feel no pain, scratching the itch eventually resulted in excavation of the lower outer border of the nose.

These cases are clearly not autotomy as commonly defined (the term is not included in either the first (Merskey, 1986) or second ( Mersky and Bogduk, 1994) edition of the IASP Classification of Chronic Pain). The term as now used in neurological/pain medicine appears to have been introduced by Wall et al. (1979), although they did not limit it to a phenomenon occurring only in supposed neuropathic pain, as now is the case.

There is an implication for experimental animal work, in which it is well-known (but rarely reported) that of animals subjected to nerve ligation and other subtotal nerve injuries, only a proportion exhibit signs of neuropathic pain, and of this proportion, only a few perform autotomy. If an animal chews off an extremity, how do we know whether it is doing so because the extremity hurts, or because it regards an anaesthetic part as a foreign body, and rids itself of it? This would appear to be the conclusion from the work of Shir et al. (2001), who found that autotomy only occurs in rats with completely denervated hindlimbs. The best argument against such an interpretation has been put forward by Blumenkopf and Lipman (1991) on the basis of animal studies, but cannot be justified by experience with human patients. The present case 2 had no pain in the mutilated area, and I do not regard it as a case of autotomy, whereas case 1 not only had pain in the mutilated area, but continued to experience such pain in the missing ala nasae after SIB, thus raising the interesting question of the relationship between pain in an area of partial sensory deficit and phantom pain.


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