Spina bifi da is a developmental condition resulting from incomplete fusion of the vertebral arches within the lumbar region. Spina bifi da occulta commonly presents asymptomatically with a tuft of hair and a small dimple in the overlying skin. More severe forms (spina bifi da cystica) are categorized into three types: Spina bifi da cystica with meningocele presents with protrusion of the meninges through the unfused vertebral arches. Spina bifi da with meningomyelocele is characterized by protrusion both of the meninges and CNS tissues and is often associated with neurologic defi cits. Rachischisis, also known as spina bifi da cystica with myeloschisis, results from a failure of neural folds to fuse and is characterized by protrusion of the spinal cord or spinal nerves and meninges.

The patient’s complaint is due to her case of hammer toes. Hammer toe can affect any toe but most commonly the second toe, then the third or fourth toes. It results most commonly from wearing shoes that are too short or shoes with heels that are too high. In hammer toe, the metatarsophalangeal joint is extended, the proximal interphalangeal joint is fl exed, and the distal phalanx points downward, looking like a hammer. Hammer toe can occur as a result of a bunion. Calluses, or painful corns, can form on the dorsal surface of the joints. In claw toe, both the proximal and distal interphalangeal joints are strongly fl exed, the result of muscle imbalance in the foot. Either hammer toe or claw toe can occur from arthritic changes. Pes cavus is the opposite of flat foot—the patient has a high, flexed plantar arch; it occurs as a result of hereditary motor and sensory neural problems. It is painful because of metatarsal compression.

22) A 23-year-old woman is admitted with severe abdominal pain, nausea, and vomiting. History taking shows that the pain is acute and has been constant for 4 days. The pain began in the epigastric region and radiated bilaterally around the chest to just below the scapulae. Currently the pain is localized in the right hypochondrium. A CT scan examination reveals calcifi ed stones in the gallbladder. Which of the following nerves is carrying the afferent fi bers of the referred pain?

The greater splanchnic nerve carries general visceral afferent fi bers from abdominal organs and can be involved in the occurrence of referred pain. The dorsal primary rami of intercostal nerves carry general somatic afferent fi bers. Pain from these fi bers would result in sharp, localized pain not dull and diffuse as occurs in referred pain. Although the phrenic nerve carries visceral afferent fi bers, it does not innervate the gallbladder. The vagus nerve carries visceral afferent f i bers that are important for visceral refl exes, but they do not transmit pain. The pelvic splanchnic nerves are parasympathetic nerves from S2 to S4 and contain visceral afferent fi bers that transmit pain from the pelvis but not from the gallbladder.

23) A 61-year-old female immigrant had been diagnosed with spinal tuberculosis. The woman had developed a fl uctuant, red, tender bulge on one fl ank, with a similar bulge in the groin on the same side. This presentation is likely due to spread of disease process within the fascia of a muscle with which of the following actions at the hip?

Spinal tuberculosis can spread within the sheath of the psoas major to its insertion with the iliacus upon the lesser trochanter, presenting there also with painful symptoms. The iliopsoas muscle is the principal fl exor of the hip joint. Abduction of the hips is performed by the gluteus medius and minimus with assistance from short lateral rotator muscles. Extension of the hip is a function of the gluteus maximus, together with the hamstring muscles. Internal rotation is performed by the adductor muscle group.

25) The 58-year-old convenience store operator had received a superfi cial bullet wound to the soft tissues on the medial side of the elbow in an attempted robbery. A major nerve was repaired at the site where it passed behind the medial epicondyle. Bleeding was stopped from an artery that accompanied the nerve in its path toward the epicondyle. Vascular repair was performed on this small artery because of its important role in supplying blood to the nerve. Which of the following arteries was most likely repaired?

The superior ulnar collateral branch of the brachial artery accompanies the ulnar nerve in its path posterior to the medial epicondyle and is important in the blood supply of the nerve. The profunda brachii passes down the arm with the radial nerve. The radial collateral artery arises from the profunda brachii and anastomoses with the radial recurrent branch of the radial artery proximal to the elbow laterally. The inferior ulnar collateral artery arises from the brachial artery and accompanies the median nerve into the forearm. The anterior ulnar recurrent artery arises from the ulnar artery and anastomoses with the inferior ulnar collateral anterior to the elbow.

27) 8 A 5-day-old infant male has an abnormally large head. A CT scan examination reveals enlarged lateral and third ventricles but a normal-size fourth ventricle. Stenosis of the cerebral aqueduct (of Sylvius) is suspected. Which of the following conditions will be characteristic of these symptoms?

Obstructive hydrocephalus, in this case resulting from obstruction of the cerebral aqueduct, refers to a condition in which fl ow of cerebrospinal fl uid (CSF) is obstructed within the ventricular system. This leads to pressure increasing in the CSF above the obstruction, explaining the enlarged lateral and third ventricles. Nonobstructive hydrocephalus is due to either excessive CSF production or ineffective CSF reabsorption. This would lead to enlargement of all ventricular chambers. Anencephaly, also known as meroanencephaly, is a partial absence of the brain and is due to defective closure of the anterior neuropore. Holoprosencephaly is a failure of cleavage of the forebrain and would result in a single fused ventricle.

28) A 2-year-old male patient develops progressive generalized weakness and muscle atrophy. The impairment first began with the muscles of the hips, and then progressed to the pelvic area, thigh, and shoulder muscles. The patient is diagnosed with Duchenne’s muscular dystrophy, a congenital disorder where the protein dystrophin is deficient. Which of the following describes the role of dystrophin in muscle tissue?

Dystrophin anchors actin to the sarcolemma, reinforcing and stabilizing the latter during muscle contraction. Titin is a large protein which associates with myosin filaments and endows them with elastic recoil properties (choice B). Desmin filaments form a supportive network extending from Z disk to Zdisk (choice C). Troponin I inhibits the binding of myosin to actin (choice D). AlphaB-crystallin protects desmin filaments from stress-induced damage (choice E).

29) An 8-year-old boy is referred to a neurologist by his family physician because he has developed progressive slow and clumsy walking. On examination, the patient has difficulty with standing and running. While standing, he adopts a wide-based gait with constant shifting of position to maintain his balance. Sitting or standing, he also displays a constant tremor of the head and trunk. When asked to walk, his feet strike the ground in an uneven and irregular rhythm; if he attempts to correct his imbalance, he displays wild and abrupt movements. A magnetic resonance image (MRI) reveals demyelination in the dorsal columns, corticospinal and spinocerebellar tracts. The child is diagnosed with Friedreich’s ataxia, an autosomal recessive neurological disorder resulting from mutation of a gene locus on chromosome 9. Second-order neurons of the dorsal (posterior) spinocerebellar tracts are located in which of the following?