424. The answer is d. (Ropper, pp 1058-1065.) Motor neuron disease in the anterior horns of the spinal cord and damage to the corticospinal tracts or motor neurons contributing axons to the corticospinal tracts would account for these neurological signs. Damage to the dorsal spinal root would be expected to produce sensory, rather than motor, deficits and would produce areflexia, rather than hyperreflexia, at the level of the injury. Damage to the ventral spinal roots would produce weakness and wasting, but no spasticity or hyperreflexia would develop. Purkinje cell damage would be expected to produce ataxia without substantial weakness. The arcuate fasciculus connects elements of the cerebral cortex not involved in the regulation of strength or motor tone.
425. The answer is b. (Ropper, pp 1223-1224.) The sausage-shaped structure in the spinal canal is a syrinx extending from C2 down into the thoracic spinal cord. This is filled with a fluid that appears similar to CSF on MRI. That this patient has syringomyelia independent of neoplasia, infarction, or intraspinal hemorrhage is suggested by the protrusion of cerebellar structures below the foramen magnum. The combination of a low-lying vermis or cerebellar tonsils and syringomyelia points to a Chiari malformation. Although it is inapparent on this MRI scan, the posterior fossa would be expected to be abnormally small, and the tentorium cerebelli would insert relatively low on the cranium. Other spinal or spinal cord problems, such as spina bifida and tethered spinal cord, would not be unusual features in association with a Chiari malformation. Even an imperforate anus might be found in the infant with a Chiari malformation, but damage to the cord sufficient to produce paraplegia is most likely with a lumbosacral myelomeningocele. With this lesion, there is a defect in the dorsal aspect of the spinal column with an attendant outpouching of meninges and neural elements from the spinal cord. Potential treatment modalities of syringes include laminectomy (to reduce damage to the spinal cord from pressure that develops between the intraspinal cyst and the vertebrae), cyst aspiration, marsupialization (slicing open and leaving open the cyst), and shunting.
426. The answer is c. (Ropper, pp 45-46.) Spinal shock is a transient phenomenon that occurs with damage to fibers from upper motor neurons. The spasticity that usually develops within a few days of the spinal cord injury is presumed to represent exaggeration of the normal stretch reflexes in the limbs disconnected from upper motor neuron control. The evolution from spinal shock to spasticity is much more typical of spinal cord injuries than it is of cerebrocortical injuries, but even with cerebrocortical injuries there is usually an interval of hours to days during which limbs that eventually become hyperreflexic and spastic are hyporeflexic and flaccid.
427. The answer is b. (Ropper, p 1313.) Winging of the scapula most often occurs with weakness of the serratus anterior muscle. This is innervated by the long thoracic nerve, whose course starts high enough and runs superficially enough to allow injury to the nerve with deep dissection into the root of the neck. The long thoracic nerve is derived from C5, C6, and C7. Winging is elicited by having the patient push against a wall with the hands at shoulder level. With this maneuver, the scapula with the weak serratus anterior will be pulled away from the back and the vertical margin of the scapula will stick out from the back. Injuries to the long thoracic nerve are usually unilateral and are often due to trauma or surgical manipulation.
428. The answer is a. (Ropper, p 196.) Extreme flexion of the lumbar spine is likely in automobile accidents and in falls in which the person is upright. Fracture of a lumbar vertebral body may be seen in vehicular accidents when the victim is restrained during a high-speed impact by a seat belt without a shoulder harness. The rapid and extreme forward flexion of the lumbar spine may produce a variety of spinal injuries, ranging from fractures to dislocations. Fractures suffered during falls in which the person is upright, such as may occur when someone jumps off a building, are usually compression fractures of the vertebral body. Fracture of the vertebral body will usually produce pain coincidental with the injury. Patients with fractures of the vertebral body that occur without trauma or with inconsequential trauma must be investigated for malignant processes, such as metastatic carcinoma, multiple myeloma, and unsuspected osteomyelitis.
429. The answer is a. (Ropper, p 158.) Hemisection of the spinal cord results in a contralateral loss of pain and thermal sensation due to spinothalamic damage and ipsilateral loss of proprioception due to posterior column damage. There is also an ipsilateral motor paralysis due to destruction of the corticospinal and rubrospinal tracts as well as motor neurons. Complete transection of the spinal cord would cause a bilateral spastic paralysis, and there would be no conscious appreciation of any cutaneous or deep sensation in the area below the transection. Posterior column syndrome would result in a bilateral loss of proprioception below the lesion, with relative preservation of pain and temperature sensation. Syringomyelic syndrome results from a lesion of the central gray matter. Pain and temperature fibers that cross at the anterior commissure are affected, which may result in bilateral loss of these sensations over several dermatomes. However, tactile sensation is spared. The most common cause of this type of syndrome is syringomyelia. Trauma, hemorrhage, or tumors are other possible etiologies. If the lesion becomes large enough, then other spinal cord systems become affected as well. Tabetic syndrome results from damage to proprioceptive and other dorsal root fibers. It is classically caused by syphilis. Symptoms include paresthesias, pain, and abnormalities of gait. Vibration sense is most affected.
430. The answer is e. (Ropper, pp 46-53.) This patient has an upper motor neuron lesion. The damage has been done proximal to the synapse of the anterior horn of the spinal cord. He will therefore develop a spastic paralysis. Fasciculations, fibrillations, flaccid paralysis, and hyporeflexia are all found following lower motor neuron lesions (at the anterior horn cell or more distally).
431. The answer is a. (Ropper, pp 148-150.) After the primary sensory fiber enters the spinal cord, the ascending branch enters the dorsal columns and travels to the medulla. The fibers from the legs and trunk travel medially in the fasciculus gracilis, whereas those from the arm and neck travel laterally in the fasciculus cuneatus. These first-order neurons synapse in the medulla, and then the second-order neurons decussate as the internal arcuate fibers and ascend in the medial lemniscus. The second-order fibers synapse in the ventroposterolateral nucleus of the thalamus, which then synapses on the somatosensory cortex.
432. The answer is e. (Aminoff, pp 37-40.) Syphilis may produce an aortic aneurysm, but this is characteristically at the level of the thoracic aorta (the arch of the aorta). With aneurysmal dilatation of the aorta, defects in the wall of the vessel may be exacerbated, and dissection of the aortic wall may develop. As this dissection extends into branches of the aorta, it usually narrows and may occlude the lumen of the vessels. Diabetes mellitus may contribute to the formation of atherosclerotic damage in the wall of the aorta, but it is the atherosclerosis itself that is most implicated in the eventual deterioration of the vascular wall. Chronic hypertension may develop with damage that involves the renal arteries, but hypertension would not be expected to be the cause of the aortic pathology.
433. The answer is e. (Aminoff, pp 37-40.) This patient probably has a spinal cord infarction from an anterior spinal artery occlusion. The posterior cord may be spared, preserving joint proprioception. Bilateral lower extremity deficits without cranial nerve or mental status findings would be an exceedingly unusual cerebral stroke presentation. There is no information, such as psychological stressors or a nonphysiologic examination, to suggest a conversion disorder in this case. MS causes neurological deficits over space and time. In this case we have a single deficit at a single point in time. History of metastatic cancer or trauma might make the physician suspect spinal cord compression.
434. The answer is d. (Ropper, p 1203.) The artery of Adamkiewicz is a major anterior radicular artery and may supply the lower two-thirds of the spinal cord. It is at risk of occlusion during abdominal aortic aneurysm repair. Other branches of the aorta or internal iliac arteries may also supply the thoracic and lumbar cord. The upper segments of the spinal cord are usually supplied off the vertebral arteries.
435. The answer is e. (Ropper, pp 127-130.) The spinothalamic system is responsible for pain and temperature sensation. It enters the spinal cord through the dorsal root ganglion. The second-order neurons then ascend one or two levels as they cross in the anterior gray commissure. Thus a lesion of the right spinothalamic tract at the T8 spinal cord level would result in a contralateral loss of pain and temperature on the left body beginning at approximately the T9-to-T10 dermatome.
436. The answer is d. (Ropper, pp 126-127.) There can be some interindividual variation; however, T10 is clearly the best choice.
437. The answer is d. (Ropper, pp 1223-1224.) A syrinx is an abnormal fluid collection resulting in an expansion of the central canal. As the lesion in this region of the spinal cord increases in size, it may affect the lower motor neuron in the anterior horn of the spinal cord, producing weakness in the distribution of the affected motor neurons. Because it is a lower motor neuron lesion, reflexes will be lost rather than increased in the upper extremities, which may at first seem counterintuitive in a spinal cord lesion. The more laterally placed corticospinal tract may be spared, leaving leg function and reflexes relatively normal. Charcot joints are the result of cumulative damage from loss of reflexes and diminished pain awareness, classically associated with syphilis or more commonly diabetes.
438. The answer is d. (Biller, p 51.) The first dorsal interosseous muscle is innervated by the ulnar nerve. The fibers of the ulnar nerve reaching this muscle originate at the C8 and T1 roots. If the ulnar nerve itself is the neural element injured, it is usually because of damage at the elbow, where the ulnar nerve runs superficially in the groove over the ulnar condyle. All the interosseous muscles of the hand are supplied by the ulnar nerve: Complete transection of that nerve will produce interosseous wasting and impaired finger adduction and abduction. Although the lumbrical muscles are situated alongside the interosseous muscles of the hand, only two lumbricals—those on the ulnar metacarpals—are innervated by the ulnar nerve. The other two lumbricals are innervated by the median nerve. All four lumbricals insert on the extensor sheaths of the fingers and participate in extension of the digits.
439. The answer is d. (Ropper, pp 1183-1185.) After cervical cord contusion, cyst formation may occur as damaged tissue is removed. This is especially likely if there has been extensive intraspinal hemorrhage. Ischemic damage may produce similar changes, but the ischemia must be substantial and persistent enough to produce infarction of spinal cord tissue. Demyelination does not lead to syringomyelia, even in cases with extensive intraspinal demyelination.
440. The answer is c. (Ropper, pp 21-25.) A number of spinal cord processes could have produced this evolving paraplegia. Rapid investigation is essential to maximize the likelihood that this young man will recover cord function once the lesion has been treated. Even a reversible lesion left untreated for days or weeks will lead to permanent disability. MRI scanning is the best emergent test when available, as it will show compressive lesions as well as processes, such as tumors, inflammation, or infection, that may affect the parenchyma of the spinal cord itself. Vascular lesions, such as spinal cord arteriovenous malformations, may also be seen on MRI, although spinal angiography is often required to confirm the lesion and guide therapy. Anticoagulation is ill advised, because any one of several processes, such as tumors, vascular malformations, or infections, may have already led to bleeding into the spinal cord or be susceptible to bleeding. The patient in the case history had schistosomiasis.
441. The answer is d. (Ropper, pp 1191, 1197.) With an intraspinal hemorrhage, the CT scan would be expected to reveal the clot as a relatively dense mass within the spinal canal. Tumors, such as meningiomas and ependymomas, should have been obvious on MRI if they were producing such dramatic symptoms and signs. Similarly, a syringomyelia should be evident as a cyst that extends over several levels of the spinal cord. With a transverse myelitis, inflammation is largely limited to the substance of the cord, and there need not be an apparent mass effect. This type of reaction may occur with a variety of noninfectious processes, such as multiple sclerosis and sarcoid, or infectious processes, such as viral and parasitic infections.
442. The answer is c. (Ropper, p 1196.) T pallidum may produce a granulomatous lesion (gumma) in the spinal cord, but this young man has an ovum in the granuloma, which suggests the much more common transverse myelitis attributable to schistosomiasis. Both S mansoni and S japonicum embolize eggs to the central nervous system (CNS), but it is S mansoni that is endemic in Puerto Rico and in locations in South America and that embolizes to the lumbar spinal cord. This patient should be treated with an anti-schistosomal agent such as praziquantel. Even with treatment, the reversal of disability produced by this spinal cord injury is usually negligible.
443. The answer is d. (Ropper, p 1203.) This patient has symptoms suggestive of ischemic spinal cord disease. The principal source of blood for the spinal cord is the aorta. Vessels that supply the cord are somewhat variable in their origins, but they most commonly arise as branches of the vertebral and hypogastric arteries, as well as of the aorta at the level of the upper and lower thoracic vertebrae. The artery most implicated in a patient with this constellation of symptoms is the great anterior medullary artery (of Adamkiewicz), which arises from the aorta at the level of T10 to L1 and supplies the anterior median spinal artery.
444. The answer is a. (Ropper, p 46.) The lateral corticospinal tract originates primarily in the precentral gyrus (primary motor cortex). These axons then travel in the posterior limb of the internal capsule and then the middle section of the cerebral peduncle. They enter the basal pons and continue as the pyramids in the medulla. At the decussation of the pyramids, the lateral corticospinal tract crosses and then continues down the spinal cord.
445. The answer is a. (Ropper, pp 1203-1205.) Spinal cord ischemia is usually most severe in the distribution of the anterior spinal artery. The posterior spinal artery is more a plexus of arteries with extensive anastomoses than a discrete pair of blood vessels running along the dorsal aspect of the spinal cord. With a lesion of the spinal cord from ischemia or pressure, the spinothalamic tracts, which are responsible for pain and temperature perception and for providing information for two-point discrimination and graphesthesia, are more vulnerable to injury than are the posterior columns. The posterior columns, which are primarily responsible for vibration and position sense, are supplied by the posterior spinal arteries.
446. The answer is c. (Ropper, pp 191-192.) With exertion, blood that would be available to the spinal cord under resting conditions might be shunted to the more patent blood vessels of the limb muscles. Unlike more typical claudication, in which leg pains develop because of poor blood flow to leg muscles, the leg pains of spinal claudication develop because of shunting of blood to the leg muscles. The pain is a reflection of ischemia to the sensory neurons in the spinal cord. Spondylolisthesis (the slippage of vertebral elements) and spondylolysis (the idiopathic dissolution of vertebral elements) may lead to pain with exertion because of the vertebral instability associated with these commonly linked conditions. However, these diagnoses should be apparent on x-ray. Myotonia and myokymia are disturbances of muscle activity that would not be expected in association with ischemic spinal cord disease.
447. The answer is c. (Ropper, pp 1203-1205.) With spinal cord infarction, as with cerebral infarction, the CSF is relatively normal. If there is an abnormality, it is most likely to be an elevated CSF protein. The gamma globulin content is not disproportionately increased, as it would be with MS. The cell count of the fluid should be normal. If the RBC content is increased, the physician must suspect hemorrhage into the CNS. An elevated WBC count suggests a wide variety of diseases, including infection, meningeal carcinomatosis, and meningeal lymphomatosis.
448. The answer is d. (Ropper, pp 1203-1205.) Collateral flow may develop with spinal cord ischemia, but the collateral supply to the anterior cord is likely to fail if the vascular system that supplies the cord is stressed. With the aortic bypass graft, pressure is reduced in the aortic aneurysm and the risks imposed by the dissection in the aortic wall may be reduced, but the pressure forcing blood through the partially obstructed artery of Adamkiewicz is also reduced. With complete failure of flow through this spinal artery, the spinal cord infarction may extend substantially and produce irreversible deficits. Bladder and bowel control is disturbed, along with the loss of strength and sensation in the legs.