112. The answer is b. (Ropper, pp 1314-1315.) Pressure on the volar aspect of the wrist may produce recurrent injuries to the carpal tunnel through which the median nerve runs. The injury characteristically produces pain and paresthesias in the hand over the distribution of the sensory component of the median nerve. This sensory distribution extends over the palmar surface of the thumb and first four digits, with the fourth digit supplied on one side by the median nerve and on the other side by the ulnar nerve. Median nerve injuries are consequently said to split the fourth digit on sensory examinations. With carpal tunnel compression of the median nerve, the sensory disturbance may be incapacitating. Subsequently, weakness and atrophy may develop in the muscles that are innervated by the median nerve. The abductor pollicis brevis may be severely involved late in the progression of the disorder. Treatment options for carpal tunnel syndrome include avoiding aggravating factors, splints, and surgical procedures. The role of surgery is not clearly defined, but many experts agree that progressive cases or those with motor involvement should often consider surgical nerve release.
113. The answer is a. (Ropper, pp 137-138.) Trauma to nerves in the extremities may give rise to causalgia, a disturbance in sensory perception characterized by hypesthesia, dysesthesia, and allodynia. Hypesthesia is a decrease in the accurate perception of stimuli. Dysesthesia is persistent discomfort, which in the situation described is likely to be an unremitting burning pain. Allodynia is the perception of pain with the application of nonpainful stimuli. Bullets and other high-velocity missiles need not hit the nerve to cause damage. Enough energy is transmitted as the missile passes through adjacent tissues to produce substantial damage to the nerve. Choices b through d involve motor or sensory findings due to either ulnar or radial nerve damage.
114. The answer is c. (Ropper, p 1315.) The ulnar nerve runs superficially at the elbow in the ulnar groove. It continues forward under the aponeurosis of the flexor carpi ulnaris in the cubital tunnel. Damage to the nerve at this site may produce weakness in the interosseous and ulnar lumbrical muscles of the hand. With lumbrical weakness, the extensor sheaths of the digits are not properly positioned, and a claw deformity with impaired extension of the ulnar two digits develops when the patient tries to straighten his or her fingers.
115. The answer is b. (Ropper, pp 282-283.) Acoustic trauma may produce severe tinnitus in persons who have relatively little hearing loss. Although the initial injury with acoustic trauma is sustained by the cochlear sensory cells, tinnitus may persist even after the acoustic nerve is cut. Tinnitus may take any one of several forms, ranging from a hissing sound to a high-pitched screaming noise.
116. The answer is c. (Ropper, p 1314.) The musculocutaneous nerve is often damaged with fractures of the humerus. This nerve supplies the biceps brachii, brachialis, and coracobrachialis muscles and carries sensory information from the lateral cutaneous nerve of the forearm. Flexion at the elbow with damage to this nerve is most impaired with the forearm supinated. The suprascapular and long thoracic are motor nerves. The radial nerve provides sensation to the dorsal-radial aspect of the forearm. The median nerve does not provide sensation to the forearm.
117. The answer is d. (Ropper, p 1314.) Radial nerve injuries are fairly common in alcoholic persons who may have lost consciousness in awkward positions. These are sometimes referred to as Saturday night palsies. The injury is usually a pressure palsy and produces a wristdrop. The nerve is injured as it courses near the spiral groove of the humerus.
118. The answer is a. (Osborn, pp I[2]:26-27.) Initially subdural blood will be denser than brain and thus readily apparent on CT scan. Within a few days of formation, the contents of a subdural hematoma are degraded into less dense fluid. This fluid is transiently similar in density to the cerebral cortex and may be difficult to distinguish by CT. Eventually it will be hypodense to brain. If the fluid collection is too small to produce substantial deformation of the underlying hemisphere, identification of the subdural collection may be difficult. Angiogram will reveal displacement of the cerebrocortical vessels, but more rapid and less invasive assessment of the patient is feasible with MRI.
119. The answer is c. (Ropper, p 858.) Something has abruptly caused increasing intracranial pressure in this young man after his head trauma. Consequently, he is at risk for herniation of the brain transfalcially (across the falx cerebri) or transtentorially (across the tentorium cerebelli). The head trauma produced an intracranial lesion, which is expanding very rapidly. The slowing of his pulse and increase in his blood pressure are due to the Cushing effect of a rapidly expanding intracranial mass. The history is typical for that of an epidural hematoma.
120. The answer is a. (Ropper, pp 805-808.) Without emergency surgery, the patient will die. Her blood pressure and pulse abnormalities will correct themselves when the intracranial mass is removed. Her loss of consciousness will not correct itself with antiepileptics. Shunt placement will not likely prevent brain herniation and may in fact accelerate it. The hematoma must be evacuated, and the bleeding giving rise to the hematoma must be stopped. Immediate treatment should include elevation of head and hyperventilation.
121. The answer is e. (Ropper, p 858.) The history is typical for an epidural hematoma. Damage to the middle meningeal artery allows blood at arterial pressures to dissect in the potential space that exists between the dura mater and the periosteum of the skull. With MRI, the epidural hematoma should be evident soon after the injury and will certainly be evident by the time the patient is symptomatic.
122. The answer is b. (Ropper, p 858.) The typical shape of an epidural hematoma is that of a biconvex mass that displaces normal brain tissue. Parts of the ventricular system may be dilated as obstructive hydrocephalus develops in parts of the system. Transfalcial herniation with displacement of frontal lobe tissue across the midline and under the falx cerebri is likely with an epidural hematoma on one side of the head. Although subdural hematomas are often bilateral, epidural hematomas are invariably unilateral.
123. The answer is c. (Ropper, p 835.) Chronic subdural hematoma is relatively common in the elderly and in patients receiving renal dialysis. The subdural fluid becomes isodense with the brain after several days or weeks and may be overlooked on CT scanning. MRI will identify the lesion, even if it is present bilaterally and produces no shift of brain structures from the midline.
124. The answer is e. (Ropper, pp 858-862.) The temporal lobes and inferior frontal lobes are frequently involved in traumatic brain injuries. The continued forward movement of the brain within the bony cranial vault, which has suddenly decelerated at impact, leads to these anterior brain structures striking the inside of the skull with great force, creating contusions in these areas. The rough surfaces of the cribriform plate and the middle cranial fossa also lead to injury in these locations. These injuries are referred to as the coup injuries because they reflect the direct blow to the brain. So-called contrecoup injury may also occur at the diametrically opposed region of the brain (generally, the occipital lobes) when there is rebound movement into the overlying skull there. Damage to the temporal lobe may produce symptoms and signs by virtue of compression of adjacent brain structures. As a hematoma expands, uncal herniation may crush the brainstem. Less progressive injuries may disturb memory or even language comprehension. Wernicke area, which is important in language comprehension, is sufficiently posterior on the temporal lobe to escape injury in most cases of frontal head trauma.
125. The answer is e. (Ropper, p 219.) Anosmia is one of the more common long-term cranial nerve deficits after head injury, though it is present in only 6% in one series. It is often associated with ageusia (loss of taste). It can be very disabling and discouraging to patients. Approximately one-third of patients recover. It is caused by avulsion of olfactory nerve rootlets due to acceleration–deceleration injury at the cribriform plate. Damage may be unilateral or bilateral.
126. The answer is b. (Ropper, pp 1187-1188.) High-dose intravenous methylprednisolone (Medrol) (30 mg/kg intravenous bolus followed by 5.4 mg/[kg-h] for 23 hours) has been shown to have a statistically significant, if clinically modest, benefit on the outcome after spinal cord injury when given within 8 hours of the injury. Naloxone hydrochloride and other agents, such as GM1 ganglioside, have not been shown to be of benefit. The role of surgical decompression, removal of hemorrhage, and correction of bone displacement is controversial. Hyperbaric chamber therapy may be useful for treatment of decompression illness (the bends).
127. The answer is a. (Biller, pp 394-396.) The patient presentation is typical for carpal tunnel syndrome. Tinel sign is the sensation of “tingling” radiating away from the percutaneous percussion of a peripheral nerve. For carpal tunnel syndrome Tinel sign of the median nerve at the wrist has ~60% sensitivity and ~67% specificity. Brudzinski and Kernig signs are indications of meningeal irritation. Monrad-Krohn test is used to confirm psychogenic upper extremity monoparesis. Babinski sign is an indication of upper motor neuron damage.