NEET PG Medical 2014

Retinoic acid in high doses is sometimes used for the treatment of skin diseases, including common acne. Retinoic acid can cause many toxic effects at high doses. The most important of these toxic effects is

• Bone demineralization, which leads to pathological fractures
• Connective tissue weakness with multiple small subcutaneous hemorrhages
• Teratogenic effects during the first trimester of pregnancy
• Peripheral neuropathy
• Amnesia

NEET PG Medical 2014

Question 6

A 27-year-old woman is involved in a motorcycle collision. She landed on her right shoulder, causing a forceful lateral extension of her head and neck. At this point, she is unable to abduct, laterally rotate, and flex the shoulder. Which injury is the most likely cause of these deficits?

• Avulsion-separation of the roots of spinal nerves C5 to C6
• Avulsion-separation of the roots of spinal nerves C8 to T1
• Injury to the medial cord of the brachial plexus
• Injury to the posterior cord of the brachial plexus
• Interruption of the C7 spinal nerve

The physical problems observed in this patient suggest an injury to more than a single nerve because no single muscle or group of muscles could cause the described deficits. In addition, the type of injury, the head and neck being forcefully pulled away from the shoulder, puts significant strain on the upper portion of the brachial plexus. Furthermore, spinal cord segments C5 and C6 innervate muscles that act on the shoulder joint. Thus, the classic result of the mechanism of injury described in this case and the resulting deficits is an avulsion-separation of the roots of spinal nerves C5 to C6.

Question 7

A 72-year-old man comes to his physician's office for his regular yearly examination. He has difficulty abducting his arm and extending his elbow and wrist. Which nervous structure is most likely injured?

• Axillary
• Lateral cord of the brachial plexus
• Posterior cord of the brachial plexus
• Radial
• Suprascapular

Loss of extension at the elbow and wrist indicates an injury to the radial nerve. However, the radial nerve is not involved in abduction of the arm. The axillary nerve is primarily responsible for abduction of the arm. Thus, the injury has to be to the part of the brachial plexus that gives rise to the axillary and radial nerves, which is the posterior cord of the brachial plexus, answer 3.

Question 8

A 32-year-old woman suffers a deep knife wound to her palm. Assuming a nerve has been severed, which of the following movements will be lost?

• Abduction of the first digit
• Adduction of the fourth digit
• Extension of the first digit
• Flexion of the distal interphalangeal joint
• Flexion of the wrist

The injury is to a nerve in the hand, and the actions described in answers 3, 4, and 5 are all accomplished by muscles coming into the hand from the forearm. Similarly, two muscles, one in the posterior compartment of the forearm and one in the thenar eminence accomplish abduction of the first digit. Although the muscle in the thenar eminence could have lost its nerve supply by this injury, the ability to abduct the first digit would not have been lost because the muscle in the forearm was not injured. The only action completely lost because of this injury would be adduction of the fourth digit, resulting from the deep branch of the ulnar nerve being cut.

Question 9

A 64-year-old man has clawing of the left hand that involves the second through fifth digits. He is also unable to actively abduct or adduct these digits. Which nervous structure is most likely injured?

• Median nerve
• Posterior trunk of the brachial plexus
• Radial nerve
• Ulnar nerve
• Upper trunk of the brachial plexus

Clawing of the hand can be related to an injury to either the ulnar or median nerves. However, an inability to abduct and adduct the second through fifth digits can only be due to an injury to the ulnar nerve, answer 4.

Question 10

While trimming a tree, a 32-year-old woman falls and hyperabducts her arm when she grabs a tree limb to stop her fall. Which area is most likely to have lost sensation because of the violent abduction of her arm?

• Thenar eminence
• Posterior brachium
• Medial antebrachium
• Lateral antebrachium
• Anterior brachium

Violent abduction of the arm, as described in this injury, results in a stretching of the lower components of the brachial plexus. This can result in an avulsion injury of the lower roots, C8 and T1, of the plexus. Cutaneous innervation to the medial brachium (arm) and medial antebrachium (forearm) passes through nerves derived from this portion of the brachial plexus and a loss of sensation could occur in these two areas as a result of this injury.

NEET Medical PG 2014

Question 1

A 62-year-old woman has a neoplasm of the left coracoid process completely compressing the axillary artery. However, the left radial arterial pulse is normal. An anastomotic connection between which of the following arteries best explains this finding?

• Anterior and posterior humeral circumflex arteries
• Subscapular and brachial arteries
• Subscapular and posterior humeral circumflex arteries
• Suprascapular and subscapular arteries
• Thoracoacromial and supreme thoracic arteries

In this case, the axillary artery is being compressed in its second part. Therefore, the anastomotic connection must be between a branch from the first part of the axillary artery, or the subclavian artery, and a branch from the third part of the axillary artery, or the brachial artery. Answer 4 is the only one that fits this requirement. The suprascapular artery is a branch of the thyrocervical trunk of the subclavian artery. It would anatomose with branches of the circumflex scapular artery, which is a branch of the subscapular artery. The subscapular artery is a branch of the third part of the axillary artery.

Question 2

A 32-year-old woman has periods of numbness of the skin covering the proximal portion of her thenar eminence. Which of the following findings will confirm the most likely diagnosis?

• Atrophy of the dorsal interosseous muscles of the hand
• Decreased strength during extension of the thumb
• Loss of sensation to the skin covering the medial aspect of the hand
• Loss of sensation to the skin of the little finger
• Weakness on attempting to compress a marble between the thumb and little finger

The cutaneous deficit reported by this patient suggests a median nerve problem. If this is the case, the patient should also have weakness or inability in flexion and opposition of the thumb. Thus, the answer describing weakness on attempting to compress a marble between the thumb and little finger would be correct. Answers 1, 3, and 4 are ulnar nerve problems, and answer 2 is a radial nerve problem.

Question 3

A 42-year-old man has impingement of the ulnar nerve at the elbow. To repair this problem, he is undergoing a medial condylar osteotomy. During the procedure, the muscular attachments to the medial epicondyle are accidentally cut. Which of the following muscles has been damaged?

• Supinator
• Flexor carpi radialis
• Brachioradialis
• Extensor carpi ulnaris
• Flexor pollicis longus

Muscles in the superficial layer of the anterior compartment of the forearm attach to the medial epicondyle of the humerus. These include the flexor carpi radialis (correct answer), palmaris longus, flexor carpi ulnaris, and pronator teres muscles.

Question 4

A 17-year-old boy suffered a severe laceration of his distal forearm. To check the ulnar pulse, the emergency department physician would palpate in which of the following locations?

• Lateral to the tendon of the flexor carpi ulnaris
• Lateral to the tendon of the flexor digitorum superficialis
• Lateral to the tendon of the palmaris longus
• Medial to the tendon of the flexor carpi ulnaris
• Medial to the tendon of the palmaris longus

The ulnar pulse is palpated lateral to the tendon of the flexor carpi ulnaris, answer 1. The radial pulse is palpated lateral to the tendon of the flexor carpi radialis.

Question 5

A 17-year-old boy is unable to extend his hand after being struck on the posterior aspect of his arm with a lacrosse stick, and there is loss of sensation in a small area on the dorsum of his hand. An x-ray film of the arm shows a midhumerus fracture. Which of the following nerves is most likely damaged?

• Axillary
• Median
• Musculocutaneous
• Radial
• Ulnar

A fracture in the middle of the humerus usually involves the radial groove, which the radial nerve occupies as it moves around the lateral aspect of the humerus. Thus, the radial nerve can be injured. The physical findings in this patient of a loss of sensation on the dorsum of his hand suggests the radial nerve has been injured.

NEET PG Medical 2014

1.

An 11-year-old male is diagnosed with leukemia 5 years after having an osteosarcoma removed from his femur and undergoing chemotherapy. His mother died from breast cancer and five other family members in his mother’s family had different cancers. Which of the following genes is the most likely candidate for the cancer in this family?

• APC
• BRCA1
• DCC
• RB1
• TP53

This patient has Li-Fraumeni syndrome, suggested by multiple types of cancers in the same family. The patient has had two different cancers. The mutation occurs in the p53 protein, which is activated by DNA damage or hypoxia to up-regulate expression of proteins participating in apoptosis. If p53 is mutated, this up-regulation cannot occur effectively, and the cell continues to divide, leading to expansion and possibly to malignancy. APC gene expression is involved in familial adenomatous polyposis. BRCA1 expression is associated with breast and ovarian cancers. The RB1 protein is also involved in the cell cycle. It binds to the E2F transcription factor to inhibit transcription, and therefore a mutation will decrease the inhibition. These cancers generally present as retinoblastomas but can also occur in other cells that receive either two spontaneous mutations or a single spontaneous mutation along with one inherited mutation (two-hit hypothesis). DCC is the “deleted in colon cancer” gene and is one of the genes mutated in the progression model of cells going from normal to abnormal to malignant.

2.

A 67-year-old female with a 1-month history of upper abdominal discomfort and weight loss (8 lb) was evaluated for a gastric ulcer. Upper gastrointestinal endoscopy revealed an area of inflammation and biopsy was negative. Computed tomography revealed a 2 × 3-cm gastric mass and a 2-cm lesion on the liver. A biopsy of the hepatic lesion was KIT-positive by immunohistochemistry and a diagnosis of gastrointestinal stromal tumor (GIST) was confirmed. Mutation of the KIT proto-oncogene resulting in tumor formation has most likely affected which molecular mechanism?

• Amplification
• Apoptosis
• Cell cycle checkpoint regulation
• Cell growth pathway
• DNA repair pathway

Students may not be familiar with the KIT mechanism of action. However, there are several clues that lead to the answer. KIT is one of the proto-oncogenes, which are typically gain-of-function mutations associated with cancers, whereas the counterpart to proto-oncogenes is tumor suppressor genes, which are typically loss-of-function mutations. Tumor suppressor proteins keep a tumor from developing by either allowing time in the cycle for repair to occur or by directing the cell to the apoptotic pathway. They are divided into cell division–controlling genes, DNA repair genes, and apoptosis genes. Options B, C, and E are therefore in the tumor suppressor, loss-of-function mutation family. KIT is a receptor tyrosine kinase, or a growth factor receptor gene, and as such if mutated leads to increased cell growth. The gene in this family that students should be best acquainted with is RET, which causes four different diseases depending on the mutation and its localization; mutations will cause both gain of function and loss of function depending upon the type and effect of the mutation. KIT is specific for GIST tumors. Option A refers to triplet repeat amplification that occurs with neurologic disorders.

3.

A 26-year-old male presents with anemia and occult blood in the stool. Flexible sigmoidoscopy reveals several polyps that are removed surgically. Family history reveals several members of the patient’s extended family developed colorectal cancer (CRC) between the ages of 25 and 70 years. The patient is concerned about the cause of colon cancer in his family. Which of the following is the most likely cause of inherited colon cancer in this family?

• Familial adenomatous polyposis
• Hereditary nonpolyposis colon cancer (HNPCC)
• Lynch II syndrome
• Peutz-Jeghers syndrome
• Unknown causes

Attention is often directed toward genetic causes of diseases and the genes involved. In these cases, FAP and HNPCC are the hallmark examples resulting from mutations in APC and mismatch repair genes. This patient has several polyps, as opposed to hundreds of polyps suggesting HNPCC. There is insufficient family history to make a better assessment about the patient, and the vast majority of CRC cases result from mutations in susceptibility genes predisposing the patient to cancer; most of these either are uncharacterized or the mechanisms of any associations between mutations and cancer are preliminary and not well understood. HNPCC is sometimes divided into Lynch I and Lynch II syndromes. The former is associated with right-sided cancer; the latter has a greater association with ovarian and endometrial cancer, among others. Peutz-Jeghers syndrome is associated with benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa.

4.

A routine ophthalmologic examination in a 20-year-old woman demonstrates several well-defined, oval, darkly pigmented lesions, one surrounded by a pale halo, on the retina. Identified as congenital hypertrophy of the retinal pigment epithelium (CHRPE), this condition is most often associated with mutations in which gene?

• APC
• BRCA1
• BRCA2
• FAP
• MLH1

CHRPE is a benign marker associated with colon cancer caused by mutations in the APC gene. FAP, or familial adenomatous polyposis, is the name of the disease caused by these mutations and not a gene itself. BRCA1 and BRCA2 genes are associated with breast and ovarian cancers.MLHI is one of the genes associated with mismatch repair defects and hereditary nonpolyposis colon cancer.

5.

A clinic diagnosed seven new cases of retinoblastoma during a 3-year period. Four cases were inherited and three were sporadic. Which of the following best distinguishes these cases?

• Both inherited and sporadic cases have tumors in both eyes.
• Both inherited and sporadic cases occur in the absence of any affected relatives.
• Inherited cases have tumors in both eyes, whereas sporadic cases have tumors in one eye.
• Two alleles are abnormal at the retinoblastoma locus in inherited retinoblastoma, but only one allele is abnormal in sporadic retinoblastoma.
• Two alleles are normal at the retinoblastoma locus in inherited retinoblastoma, but only one allele is normal in sporadic retinoblastoma.

Retinoblastoma is the model disease for explaining the two-hit hypothesis and tumor suppressor gene mutations. It normally causes confusion for students because tumor suppressor mutations are “inherited in an autosomal dominant manner but expressed in an autosomal recessive manner.” Most individuals who inherit one mutated allele develop a mutation in the normal allele and express the disease; those who do not express the disease demonstrate incomplete penetrance. For those individuals inheriting two normal alleles, it is much less likely that two mutations will occur in the RB alleles. When the latter occurs, it is usually in adults; cancers may often demonstrate mutated RB alleles as a consequence of rapid proliferation and decreased effective time for repair. In this case, children are developing Rb, suggesting they inherited a mutated allele. Inherited cases tend to have tumors in both eyes because all cells inherited the same mutated allele. Sporadic cases tend to have cancers in only one eye because it would require four independent events in the same alleles in two places to develop tumors. Since all cases are children, the leading question is what might be causing an increase in sporadic Rb at this age.

Hemostasis

Wounds often bleed actively, particularly during assessment and exploration. In addition to the problem of adequate wound visualization with active bleeding, hematomas can cause an increase in the rate of wound infection and can delay the healing process.

The simplest and most effective way to stop bleeding is to apply direct pressure to the wound with handheld surgical 4 × 4 sponges. Continuous pressure has to be applied for a minimum of 10 minutes. Because of the time involved, sponges secured with an Ace wrap can be substituted if the wound is in an anatomic area that lends itself to wrapping.

An epinephrine-moistened (1:100,000) sponge applied, also with pressure, to the wound for 5 minutes often suffices in cases in which direct pressure fails. Epinephrine is contraindicated, however, for use on the fingers, toes, ears, penis, and tip of the nose. Packing the wound with topical hemostatic agents, such as Gelfoam, Surgicel, and others, is another hemostatic strategy. These agents are useful for persistent oozing or minor capillary bleeding. Arterial “pumpers,” even small ones, can wash these agents out of the wound. Use of these agents should be considered only if all other methods fail. These products can have adverse effects such as interference with suture closure and foreign-body reactions.

Direct clamping with a hemostat and a hand-tied ligature with an absorbable suture is reserved for larger, single-bleeding vessels that can be directly visualized under optimal conditions of lighting, instrument preparation, and operator comfort. Because blood vessels often travel with nerves and arteries, “blind” clamping in a bleeding wound, in the hope of grasping the bleeder, is strongly discouraged. Unnecessary tissue damage can occur, particularly in areas where important structures such as nerves and tendons are likely to be found.

Tourniquet Hemostasis

Definitive hemostasis of the extremity can be achieved by the use of tourniquets. Strict observance of proper technique and the time limits of application is imperative. Complications of tourniquets include ischemia of the extremity, compression damage of blood vessels and nerves, and jeopardy to marginally viable tissues.

Technique for Large-Extremity Tourniquet Application

Before placing a single-cuff sphygmomanometer, the extremity is elevated for approximately 1 minute. The cuff is inflated to a pressure higher than the patient’s systolic pressure or to a point when the bleeding stops. However, the pressure should not exceed 250 mm Hg. The clinician clamps the cuff tubing with a hemostat instead of closing the air release valve to prevent slow leakage of air and to ensure a rapid release method if needed. Patient discomfort becomes apparent by 30 to 45 minutes of cuff time.¹¹ The maximal cuff inflation time is 2 hours, although a limit of 30 to 60 minutes is recommended to ensure patient safety.

Technique for Digital Tourniquet Application

A digital tourniquet is often used to repair finger wounds. Lacerated fingers can bleed profusely and visualization is difficult. The clinician unfolds a 4 × 4 gauze sponge to its fullest length and folds it in half so it appears to be an 8-inch band. The band is moistened with saline. The clinician wraps the band firmly around the finger, starting at the tip and proceeding to the base. A Penrose drain is stretched around the base of the finger in a slinglike fashion, and a hemostat is applied to the drain to form a tight “ring” at the base of the finger. The sponge wrapping is removed. A Penrose drain also can be substituted for the gauze sponge wrap. A digital anesthetic block is recommended before applying the tourniquet.

There are preformed disposable tourniquets (Tourni-Cot, T-Ring) that “roll” or slide onto the finger and exsanguinate it before coming to rest at the digit base.After use, they can be easily removed. These tourniquets are easier to apply and are effective in most cases in which the digit circumference can accommodate them. The maximal allowable tourniquet time for a finger is 20 to 30 minutes.

 Ref-

Wounds and Lacerations: Emergency Care and Closure

by Alexander T. Trott

4th edition published by Elsevier