(a) Lesions of the cauda equina (by tumors, caries, or fracture of the bones, etc.) produce paralysis, anæsthesia, atrophy of muscles, with De R., in the range of distribution of the sciatic nerves mainly. The sphincter ani is paralyzed and relaxed, while the bladder remains normal as a rule. In all essential respects this paraplegiform, but not paraplegic, affection resembles that following injury to mixed nerve-trunks. It is in reality an intra-spinal peripheral paralysis. The more exact location of the lesion, in the absence of external physical signs (fracture, etc.), may be approximately determined by a study of the distribution of the symptoms and their relation to nerve-supply.
(b) Lesions of the lower end of the lumbar enlargement, or conus medullaris, behind the first lumbar vertebra, will give rise to the same symptoms as (a). The expression, lumbar part of the spinal cord, should be more carefully used than it is at present in the discussion of spinal injuries and spinal-cord diseases, disease of the lumbar enlargement being common enough, but disease of the lumbar part of the cord very rare. In the discussion of railway cases, more especially, it is often forgotten that the spinal cord practically ends behind the first lumbar vertebra.
(c) Lesions of the middle and upper parts (segments) of the lumbar enlargement are evidenced by true paraplegia, without paralysis of the abdominal muscles. In some cases the quadriceps group, supplied by the crural nerve, is not paralyzed. The constriction and the limit of anæsthesia are about the knees, at mid-thigh, or near the groin in different cases. The paralyzed muscles, as a rule, retain their irritability and show normal electrical reactions; the cutaneous and tendinous reflexes are preserved or increased. The sphincter is usually paralyzed, while the bladder is relatively unaffected.
(d) Transverse lesion of the dorsal spinal cord produces the classical type of paraplegia—i.e. paralysis and anæsthesia of all parts caudad of the lesion. The limit of anæsthesia and the constriction band are nearly horizontal, and their exact level varies with the height of the lesion, from the hypogastric region to above the nipples. Below the level of anæsthesia, which indicates by the number of the dorsal nerve the upper limit of the cord lesion, there are complete paralysis, retention of urine, constipation with relaxed sphincter ani, greatly exaggerated reflexes in the lower extremities, even to spinal epilepsy; the muscles preserve their volume fairly well, and their electrical reactions are normal—sensibility in all its modes is abolished; bed-sores are easily provoked. Retention of urine is an early symptom in lesion of the middle dorsal region of the cord—sometimes, in our experience, preceding symptoms in the legs.
(e) A transverse lesion of the cord at the level of the last cervical and first dorsal nerves—i.e. in the lower part of the cervical enlargement—gives rise to typical paraplegia with a sensory limit-line at or just below the clavicle, but also with some very peculiar symptoms superadded. These characteristic symptoms are in the upper extremities, and consist of paralysis and anæsthesia in the range of distribution of the ulnar nerves. In the arms the anæsthesia will be found along the lower ulnar aspect of the forearm, the ulnar part of the hands, the whole of the little fingers, and one half of the annuli. There will be paralysis (and in some cases atrophy with De R.) affecting the flexor carpi ulnaris, the hypothenar eminence, the interossei, and the ulnar half of the thenar group of muscles, producing in most cases a special deformity of the hand known as claw-hand or main-en-griffe. Another important symptom of a transverse lesion in this location is complete paralysis of all the intercostal and abdominal muscles, rendering respiration diaphragmatic and making coughing and expectoration impossible. The breathing is abdominal in type, and asphyxia is constantly impending.
(f) A transverse lesion of the upper part of the cervical enlargement, below the origin of the fourth cervical nerve, gives rise to symptoms designated as cervical or total paraplegia. The lower extremities and trunk are as in (d) and (e), but besides both arms are completely paralyzed and anæsthetic. The limit of anæsthesia usually extends along the clavicles to the acromion processes, or a little below, near the deltoid insertions. All reflexes caudad of this line are vastly increased, either with tonic or clonic contractions. In some cases of pressure upon the cervical cord by tumors, caries of vertebræ, etc. the tetanoid or spastic state of the extremities (the lower more especially) may precede paralysis for a long time; as the compression increases paralysis becomes more and more marked, while the reflexes remain high. This constitutes the clinical group we described in 1873 as tetanoid pseudo-paraplegia.
(g) Transverse lesions of the spinal cord from the decussation of the pyramids to the fourth cervical nerve are very rare, and usually of traumatic origin. They produce complete paralysis of the entire body, and also of the diaphragm (third and fourth cervical nerves), thus causing death by apnœa in a very short time.
(h) In ascending paralysis (Landry) the above symptom-groups, excepting (a), (b), are met with at successive stages of the disease, often by almost daily accession, until finally respiration ceases.
(i) The height of a transverse localized lesion (e.g. a stab-wound) of one lateral half of the spinal cord is to be determined by the various groupings of symptoms stated in the preceding paragraphs, the chief guide being the limit-line between the sensitive and anæsthetic portions of the body, measured vertically. The symptoms are, however, distributed in a very remarkable manner on either side of the median line. The paralysis will be found on the same side as the lesion, often accompanied by hyperæsthesia, vaso-motor paralysis, and loss of muscular sense, while the anæsthesia is on the other side of the body. When such a lesion occurs below the first dorsal nerve, the symptom-group is designated as hemiparaplegia; when the lesion is higher up, so as to paralyze the arms, the affection is termed spinal hemiplegia (Brown-Séquard).
Above the decussation of the pyramids total transverse lesions are practically unknown, so that the second question need not be followed farther.