Central pruritus. Case report

Pain, 45 (1991) 307-308 0 1991 Elsevier Science Publishers ADONIS

307 B.V. 0304-3959/91/$03.50

030439599100139H

PAIN 01851

Clinical Note

Central pruritus. Case report Paolo Procacci and Marco Maresca Pain Center, University of Florence, 50134 Florence (Italy) (Received

7 January

1991, revision received

31 January

1991, accepted

An 82-year-old woman experienced generalized pruritus not Summary Scratching the skin with a needle induced a crisis of intense pruritus, insensitive characteristics of a central sensation. Key words: Generalized

pruritus;

Central

9 February

1991)

due to skin or systemic to any drug. The pruritus

disease. had the

sensation

Introduction According to Wall (personal communication), the term ‘thalamic pain syndrome’ is an unfortunate misnomer. First, it is not obviously ‘thalamic.’ Second, patients suffering a peculiar unpleasant sensation may opt for the word ‘pain’ as the nearest word in their vocabulary even though it is nothing like any pain they have previously experienced. Perhaps the patient we describe opted for the word pruritus in this way.

Case report A Caucasian female (named A.T., aged 82) entered the Institute for Clinical Medicine I, at the University of Florence, with the complaint of intense generalized pruritus. This symptom started suddenly 2 years before on the left side of the body and was not associated with skin or systemic disease. No transient ischaemic attack (TIA) or other neurological sign was reported. After some months, the pruritus spread to include the right side of the body. The pruritus was intense with a clear circadian variation (stronger in the early morning). No dermatological lesion was present; for this reason we speak of pruritus instead of itch, following the criterion

Correspondence to: Prof. Paolo Procacci, Servizio di Algologia, Istituto di Clinica Medica I, Universita di Firenze, Viale G.B. Morgagni 85, 50134 Florence, Italy.

in the Cecil Textbook of Medicine: ‘generalized itching in the absence of primary skin disease’ [4]. Careful examination showed that the well known causes of pruritus in internal medicine were absent [4]. A CT scan of the brain was normal and an MR scan did not reveal any lesion in the CNS. The patient showed signs of repetitive scratching over the whole body. Many antihistaminic and psychotropic drugs were administered without any change in her pruritus. When we were called to examine the patient, she told us that her pruritus was less intense at that moment. We began our clinical observation on the volar left forearm where the skin was intact and free from scratches. Digital pressure did not cause any variation in the pruritus. We began to scratch the skin with a needle, a common semeiologic manoeuvre to assess possible variations in sensibility. After about 3 cm of scratching, severe pain was felt in the forearm with the classic characteristics of hyperpathia. A crisis of ‘terrible’ (patient’s word) pruritus exploded over the whole body, the worst the subject had felt in 2 years. The crisis lasted about 2 h and the patient was unresponsive to any drug, including narcotic analgesics. Because she refused to be further examined, we could test neither the effect of Von Frey’s bristles on the skin of the muco-cutaneous junction on the lips nor the effect of electric current. The patient was dismissed from the clinic with a therapy of antihistaminic and neuroleptic drugs: dexchlorpheniramine maleate (Polaramin@, Essex, tablets) and pimozide (Orap@, Janssen, tablets). The sensorium was slightly obtunded, but the pruritus remained.

30X

Discussion We discussed this case with C.A. Pagni, whose extensive experience with central pain states is well known. He had never observed a case like ours. In his neurosurgical experience, pruritus had only appeared in a few cases of retrogasserian section for intractable trigeminal neuralgia. Pruritus had been confined to the ipsilateral skin of the nose, scratching being so intense as to provoke ulcers. In our patient pruritus had the classic characteristics of a central sensation like pain in the Dejerine-Roussy syndrome: sudden onset, diffusion to a hemisoma and transfer of pain to the contralateral hemisoma, as happens in some cases. Possible central pain mechanisms were recently discussed by Tasker and Dostrovsky [6], Pagni [3] and Bonica [l]. As regards itch, there is a general agreement that it is signalled by C fibres [2,7,8], but a specific cutaneous receptor responding preferentially to pruritic agents has not been identified [2]. According to Tuckett [7], receptors responding to an itch-producing substance have the characteristics of C fibre, mechano-heat nociceptors. The central process leading to the sensation of itching remains unknown. The old hypothesis that pruritus can be a sort of subliminal pain seems supported by our case. In fact, when pain arose after stimulation, an intense pruritus exploded over the whole body with the characteristics of

a central sensation. Consequently, we have classified this case as ‘central pruritus.’ The relationship between pain and itch, studied intensively 30 years ago ]S.X]. should be carefully considered again in the 1990s.

References 1 Bonica, J.J., The Management of Pain. 2nd edn.. Lea and Febiger, Philadelphia, PA, 1990, 2120 pp. 2 Campbell, J.N., Raja, S.N., Cohen, R.H., Manning, D.C., Khan. A.A. and Meyer, R.A.. Peripheral neural mechanisms of nociception. In: P.D. Wall and R. Melzack (Eds.), Textbook of Pain. 2nd edn.. Churchill Livingstone, Edinburgh, 1989, pp. 22-45. 3 Pagni, C.A.. Central pain due to spinal cord and brain stem damage. In: P.D. Wall and R. Melzack (Eds.), Textbook of Pain. 2nd edn., Churchill Livingstone, Edinburgh, 1989, pp. 634-655. 4 Parker, F.. Skin diseases. In: J.B. Wyngaarden and L.H. Smith, Jr. (Eds.), Cecil Textbook of Medicine, 18th edn.. Saunders, Philadelphia, PA, 1988. pp. 2300-2353. 5 Rothman, S., Pathophysiology of itch sensation. In: W. Montagna (Ed.), Cutaneous Innervation, Pergamon Press, Oxford, 1960, pp. 1899200. 6 Tasker, R.R. and Dostrovsky, J.O., Deafferentation and central pain. In: P.D. Wall and R. Melzack (Eds.), Textbook of Pain. 2nd edn., Churchill Livingstone, Edinburgh, 1989. pp. 154-180. 7 Tuckett. R.P., Itch evoked by electrical stimulation of the skin, J. Invest. Dermatol., 79 (1982) 368-373. 8 Wolstenholme, G.E.W. and O’Connor, M. (Eds.). Pain and Itch. Churchill. London, 1959, 120 pp.