(b) Lesions of the spinal pyramidal tract (of fasciculi 10 and 11) are followed by motor symptoms only—viz. paralysis and contracture—or, in other words, by a spastic paralysis. Sensibility is unaffected; the bladder, rectum, and truncal muscles are not distinctly paralyzed; the reflexes are much increased, and ankle-clonus is often present. The electrical reactions of the paralyzed muscles are normal, qualitatively at least. The diagnosis of localization may be pushed still farther by the following considerations:
(1) When the condition of spastic paralysis is unilateral, of hemiplegic distribution, and follows an attack of cerebral disease of some sort, we may feel sure that both the crossed and the direct fasciculi of the pyramidal (10 and 11) belonging to one cerebral motor tract are degenerated throughout the length of the spinal cord, the crossed fasciculus on the paralyzed side and the direct on the healthy side (same side as injured hemisphere). It would thus appear that lesion of the direct pyramidal fasciculus (11) produces no symptoms,4 except, of course, in those rare cases in which it is larger than its associated crossed fasciculus.
4 Unless it be the increase of reflexes which is so often observed on the non-paralyzed side in hemiplegics.
(2) The above symptoms may be bilateral, as observed in children as a congenital or early-acquired condition. In such cases the four fasciculi of the motor tract are degenerated or undeveloped, in correspondence with a symmetrical bilateral lesion of the motor area of the cerebrum—imperfect development or early destruction.
(3) When the legs alone are the seat of spastic paralysis, with increased reflexes, spastic or tetanoid gait, without sensory symptoms, the diagnosis of a primary sclerosis of both lateral columns (inclusive of 10) of the spinal cord is justified.
(c) Lesions of antero-lateral columns of the cord (8 and 12), primary and independent of lesions of the anterior horns or of the crossed pyramidal fasciculus, cannot now be diagnosticated during life. These large masses of fibres include fasciculi whose functions are probably motor; others (especially in 12) whose functions, according to recent experiments, may be sensory; and still others which are associating or commissural.
(d) Various combinations of the above lesions occur, and may be recognized positively during life: (1) Combined sclerosis of the posterior columns and of the crossed pyramidal fasciculi (3 and 10), indicated by ataxia with paralysis, absence of patellar reflex, tendency to contracture, pains, and anæsthesia less marked than in typical posterior spinal sclerosis. This symptom-group is usually found in children; it is pre-eminently a family disease, and is known as Friedreich's disease. Similar cases also occur in adults as a strictly personal disease. (2) Secondary degeneration of the pyramidal tract (10 and 11), with more or less localized atrophy of cells in the anterior horns (9) coexists in two forms: First, in a few cases of cerebral hemiplegia with contracture, and pathological atrophy of various muscles on the paralyzed side; second, as a distinctly spinal bilateral affection, characterized by a spastic or tetanoid state of the lower extremities, and a mixture of atrophic paralysis (vide (a)), with contracture in the arms and hands. This latter form is the amyotrophic lateral sclerosis of Charcot.
SECOND QUESTION.—BEING GIVEN SYMPTOMS INDICATING A TOTAL TRANSVERSE LESION OF THE SPINAL CORD, ONE INVOLVING ITS VARIOUS SYSTEMS AT A CERTAIN LEVEL, TO DETERMINE THE ELEVATION OR FRONTO-CAUDAL SITUATION OF THE LESION.
This question is usually easy of solution by the following method: Since a transverse lesion of the spinal cord gives rise to both motor and sensory symptoms of horizontal, paraplegic distribution caudad of the lesion, the first thing to do is to determine accurately the upper level of the symptom, either the line of anæsthesia or the limit of paralysis. The former is always much more definite than the latter, and usually serves as the guide to diagnosis, indicating accurately the uppermost part of the lesion. In the thorax the levels of sensory and motor symptoms nearly coincide, but in the extremities the operation of Van der Kolk's law of distribution of motor and sensory fibres of nerve-trunks must be borne in mind, although it does not apply as strictly in this case as in nerve lesions strictly speaking. Gowers's diagram will prove very serviceable in making a diagnosis of transverse lesions, and will also prove of use in the study of vertebral injury and disease, as it indicates with sufficient accuracy the relation between vertebræ (spinous processes) and segments of the spinal cord. (Vide [Fig. 2.])
The following are the principal transverse localizations of disease which are usually recognized during life by the above procedure: