ROYAL SOCIETY OF MEDICINE

1022

ROYAL SOCIETY OF MEDICINE

SECTION OF NEUROLOGY

BEFORE this section on Oct. 21st Dr. ANTHONYFEILING delivered a presidential address entitled

Central Pain in Spinal Cord LesionsThe term " central pain," he explained, was generallyrestricted to pain associated with lesions in the sub-stance of the central nervous system. Cases of realcentral pain exhibited three chief features : spon-taneity, persistence, and a more or less constantdistribution in each case.

Persistent central pain was not common in spinalcord injuries, but striking examples had been seen inthe late war. Holmes had noted that in all casesthe pains were spontaneous but much aggravatedby external stimuli, especially movements of theaffected parts, vibrations, and even light. Severe

pain was often referred to distant parts below thelevel of the wound. Hyperaesthesia was sometimesmore persistent than the pain itself. The severitygenerally abated in two or three weeks. In unilateral

injury the pain was felt chiefly on the paralysedside. The injury was mostly in the cervical part ofthe cord. The pain might arise from severe con-cussion or commotion effects without any directexternal wound. Severe pain from injuries of thecervical part were often referred to the arms, especi-ally in the distribution of the eighth cervical and firstdorsal segments. Hypersesthesia might persist forsome time. Lhermitte had distinguished other formsof pain, including hyperalgesia to cutaneous stimuli,electric shock-like pain provoked by movement, andpain recalling that of tabes. The more severe the

spinal injury the less likely were central pains to befelt. They were almost unknown where paraplegiawas complete and prolonged, and were not generallyassociated with very slight spinal injuries where

paralysis was only transitory. The lesion whichusually caused them was a moderate damage tothe cord short of complete interruption of function.

Pain was a well-recognised early symptom in

spinal cord tumours. Dr. Feiling referred especially,however, to a class of pain which he had found tobe more frequent in cases of extra- and intra-medullarytumour than was commonly believed : pains referredto distant parts and areas not supplied with sensa-tion from the nerve at the level of the lesion. These

pains hardly seemed to have received the attentionthey deserved. In several cases the earliest com-

plaint had been of pain in the legs, not of a radiculartype and most often referred to the distal parts ofthe legs, when a tumour was present considerablyabove the lumbar region. Intramedullary tumoursoccasionally produced very intense, persistent, widelydistributed, and intractable pain.Although pain was usually considered to be absent

in syringomyelia, he believed that it might be anearly symptom. Some patients complained of

burning, cutting, or painful cold. As a rule it wasreferred to areas innervated only from the cervicaland upper dorsal regions of the cord. The shoulder,arms, and upper thorax were most affected, and insome cases the pain was entirely unilateral. Wherethe pains were confined to the upper extremities andtrunk they were usually associated with both hypo-algesia and loss or diminution of thermal sensibility.Persistent pains were sometimes referred to the legs.He doubted whether the pains in syringomyelia werereally due to distention of cavities in the cord. Theresults of operation were far from uniformly success-ful, and gross enlargement could exist without pain.

His present conclusions were that X rays were thefirst treatment of choice and operation the second.Simple incision of the cord was generally soon fol-lowed by a return of the pain, and more successmight be hoped for from complete division of thecord in the middle line over a number of segments,to ensure that the fibres crossing the middle line andcarrying sensations of pain would be divided.

Similar types of subjective disorders of sensationmight exist in disseminated sclerosis and in subacutecombined degeneration. Paraesthesiae were apt to bemore persistent and prominent in the latter syndrome,and assumed every conceivable form. Less often,but much more commonly in subacute combineddegeneration, the patient complained of peculiarthermal dysaesthesiae, especially a feeling of intensecold. Sensations of heat or warmth were veryunusual. It was not always easy to distinguishbetween the pains and the dysaesthesiae. Real severe

pains were uncommon in both conditions but

undoubtedly occurred. In disseminated sclerosis theywere most often an early symptom and affectedespecially the legs. They were spontaneous but notcontinuous, occurred as a rule in paroxysms lastinga few days, and were sometimes likened to toothacheand sometimes to electric shock. They occasionallyresembled sciatica, and in some cases had a girdledistribution. Severe trigeminal pain was sometimesfelt in disseminated sclerosis. Girdle sensations andpains were also not uncommon in subacute combineddegeneration, and quite a number of patients com-plained of severe pains in the legs. As, however,degenerative changes occurred in the peripheralnerves, the physician must be cautious in assumingthat the origin was in the spinal cord. Some ofthe most obstinate cases of central pain had beenassociated with a reliable diagnosis of vascular lesion.

Tabes dorsalis was more apt than any other diseaseof the cord to cause striking and characteristic pains.All agreed that the essential lesion was a degen-eration of certain exogenous fibres of the posteriorroot. The crucial question was at which point theafferent neurone was first attacked, and Dr. Feilingdeclared his belief in the earlier conception that thefirst changes occurred in the intraspinal course ofthe nerve-fibre. If this were true, then the classicpains of tabes might be regarded as a form of centralpain. Changes in the peripheral nerve could notbe absolutely excluded, but other peripheral nervelesions very rarely produced pain of the same characterand persistence. n - - - --

The only factor common to all the different con-ditions in which central pain was observed was analteration in the physical state of the nerve-fibres.Many of these must be destroyed entirely, and manymust be in a state of degeneration or slow death.The central pains were in some cases referred to

parts which were normally sensitive to objectivetesting of sensation, and in other cases to insensitiveparts. Moreover, while they were sometimes referredonly to parts innervated from the segmental levelof the lesion, in other cases they were referred to

parts distant from the site of the lesion. Afferentpaths carrying sensation must therefore still be func-tioning between the site of the lesion and the highercentres. Noxious stimuli directly applied to certainparts of the spinal cord in fact produced pain. Whileadmitting that the conception of a permanent oreven long-standing focus of irritation or stimuliwas somewhat unsatisfactory, Dr. Feiling believedthat it was still the most probable explanation ofthese pains. He could not say why pain was entirelyabsent in some cases and permanent in others.