This is the basis for the so-called bulbar and paraplegic types. In certain cases, trophic symptoms predominate, due, it has been thought, to a complicating ritis. Morvan's disease is assumed by many to be essentially identical with this form of syringomyelia. The identity has not yet been proved, although the clin ical resemblance is certainly strikingly suggestive.
From a study of over five hundred papers which have been published on syringamyclia, it was found that the following are some of the more charac teristic features besides those of progress ive muscular atrophy and paraplegia :- 1. The arthropathies of syringomyelia may be divided into two classes: the atrophic, which is the rarer; and the • hypertrophic, which in many ways re sembles osteoarthritis. These changes in the joints are much more frequent in the upper than in the lower extremities.
2. In 50 per cent. of the cases there is more or less deviation of the spinal column, usually laterally; one type of deformity being shown in the above figure.
3. 'Vasomotor disturbances are often well marked, particularly by sensation of cold and local areas with excessive sweating.
4. The action of the sphincters is gen erally normal.
5. Ocular symptoms: Pupils are fre quently unequal. Nystagmus has been occasionally noted. Optic disks are gen erally normal.
6. When the medulla is invaded by the glioma, bulbar symptoms ensue, particu larly laryngeal paralysis, while the in volvement of the several nerves arising from the pons and medulla will cause corresponding symptoms.
The most characteristic symptoms are due to degenerative changes in the pos terior horns of the cord, more particu larly the disassociation of thermo-ans thesia from defects of the other sensa tions. Innsdale (Inter. Med. Mag., Jan., '97).
The boat-shaped deformity of the tho rax, met with in sonic eases of syringo myelia, consists in a characteristic de pression of the central portion of the an terior wall of the chest above the lower margins of the great pectoral muscles, on either side of which the chest-wall rises, so that the shoulders appear to be brought forward. This depression is a trophic lesion analogous to those affect ing other parts of the skeleton in the same disease. Asti6 (These de Paris, No. 225, '96-'97).
Diagnosis.—With our present knowl edge, or rather lack of it, an inaccurate diagnosis in syringomyelia is not a ous reflection upon individual skill. Of
the affections with which it is most likely to be confounded, tumor and Irzemor rhage of the cord, myelitis, pachymenin gitis, particularly cervicalis hypertro phica, progressive muscular atrophy, and tabes dorsalis are chief in importance. In tumor all irritative symptoms—such as pain, spasm, etc.—are usually far more pronounced, the symptoms are more definitely localized and unilateral, and the rate of progress is more rapid. Tu mor elsewhere, especially if malignant, is significant. In cord limmorrhage or embolism the onset is abrupt and apo plectiform in nature and the symptoms are rapidly destructive. From myelitis the diagnosis may be, at times, difficult. The more widely distributed symptoms and the more extensive involvement of all forms of sensation, with the relative infrequency of true trophic symptoms in myelitis, should prove sufficient data. The muscular atrophy is often late in myelitis and is more rapid after once beginning. From cervical pachymenin gitis the differential diagnosis is at times impossible during life. It is only when tabes dorsalis begins with extensive and vicious trophic symptoms or when, as has been noted occasionally, a tabetic pre sents the symptom of dissociated sensa tion that any temporary hesitancy be tween the two diseases occurs. In lep rosy we may have analgesia and severe trophic lesions, but there is no atrophy, scoliosis, or dissociated sensation as in syringomyelia.
Etiology. — The disease is compara tively rare. More cases have been re ported among males than females and a large percentage of reported cases have been recognized first between the ages of 25 and 35 years. The essential causative factor is an inherent predisposition dat ing back to embryonal life. Syringo myelia is not directly hereditary nor is it a "family" disease. No adequate or satis factory explanation has been offered for the cause of the developmental defect which primarily underlies the disease. Cleft palate, harelip, spina bifida, and other similar defects afford probable analogies. The exciting cause is most often trauma. Prolonged exposure to severe cold and dampness, overexertion physically, toxminias, malnutrition, and anmmia are some of the contributory or exciting causes to which individual cases have been ascribed. Syphilis and alco holism may be indirect etiological factors.