Chapter 16 Patient Positioning and Associated Risks
1. Whose responsibility is the intraoperative position of the anesthetized patient?
2. How does the lack of response to pain affect the positions that are tolerated by patients under general anesthesia? What is the clinical implication of this?
3. What are potential injuries to the patient that can be sustained during mask ventilation of the airway?
4. What areas of skin are especially prone to ischemic damage during surgery? How can this risk be minimized?
Specific positions
5. What are the cardiovascular effects of placing the patient in the supine position for a surgical procedure?
6. How does the supine position affect lung perfusion?
7. How does the functional residual capacity change when a patient’s position is changed from standing to supine?
8. How should the patient’s legs be ideally positioned during surgery in the supine position?
9. Why might focal alopecia result following surgery?
10. Why might backache result from surgery in the supine position?
11. What are some potential positions the patient’s arms may be placed in while the patient is in the supine position for surgery?
12. Describe how the patient’s arms should be positioned when the patient is supine and the arms are abducted.
13. Describe how the patient’s arms should be positioned when the patient is supine and the arms are adducted.
14. What are the cardiovascular effects of placing the patient in the head-down position, or Trendelenburg position, for a surgical procedure?
15. What are the pulmonary effects of placing the patient in the Trendelenburg position for a surgical procedure?
16. How does the Trendelenburg position affect the patient’s intracranial pressure?
17. What is a potential complication of the use of shoulder braces to prevent the patient from sliding off the table while in a steep Trendelenburg position?
18. How does the prone position affect the patient’s ventilatory mechanics? How can this effect be offset?
19. What are the cardiovascular effects of placing the patient in the prone position for a surgical procedure? How can this potential problem be minimized?
20. What are the potential problems with turning the prone patient’s head laterally?
21. What is a potential problem with placing the prone patient’s head in a neutral forward-facing position, as in a Mayfield headrest? How can this potential problem be minimized?
22. How should the patient’s arms be positioned while in the prone position?
23. How can venous pooling in the lower extremities be offset while the patient is in the prone position, as during a laminectomy?
24. How does the lateral decubitus position affect the patient’s ventilatory mechanics and ventilation-perfusion ratio during mechanical ventilation of the lungs? How might these effects of the lateral decubitus position be manifest clinically?
25. What are the cardiovascular effects of placing the patient in the lateral decubitus position for a surgical procedure?
26. What is the purpose of the axillary roll for patients who are placed in the lateral decubitus position? What monitoring may be helpful?
27. How should the patient’s head and neck be positioned when in the lateral decubitus position?
28. How should the patient’s legs be positioned when in the lateral decubitus position?
29. How should the patient’s nondependent arm be positioned when in the lateral decubitus position?
30. For what types of surgery is the sitting position most often used?
31. What are the cardiovascular effects of placing the patient in the sitting position for a surgical procedure?
32. What is the principal potential intraoperative complication of positioning a patient in the sitting position for surgery?
33. Which patients are most likely to manifest cardiopulmonary effects from being placed in the lithotomy position for a surgical procedure?
34. How should a patient with a history of low back pain be positioned in the lithotomy position for surgery?
35. What is the principal potential intraoperative complication of positioning a patient in the lithotomy position for surgery? How can this potential problem be minimized?
36. What is a potential problem that can result from placing a patient in the lithotomy position for more than 4 hours during a surgical procedure?
37. How can the patient’s digits of the fingers or toes be injured during moving of operating table parts?
Peripheral nerve injury
38. How important are peripheral nerve injuries? During what types of anesthetics do peripheral nerve injuries occur? What is the mechanism of a peripheral nerve injury during surgery? How can this risk be minimized?
39. What are some coexisting medical conditions that place a patient at an increased risk for a peripheral nerve injury?
40. What is the usual recovery time from a peripheral nerve injury?
41. Which peripheral nerve is most likely to manifest a postoperative neuropathy?
42. What are some ways in which the ulnar nerve may be injured intraoperatively? What position should a patient’s arm be placed in to minimize this risk?
43. Are males or females more prone to ulnar nerve injury during surgery?
44. How does injury to the ulnar nerve manifest clinically?
45. What is the second most common peripheral nerve injured during surgery?
46. Why is the brachial plexus especially susceptible to nerve injury during surgery?
47. What are some ways in which the brachial plexus may be injured intraoperatively?
48. How does injury to the brachial plexus manifest clinically?
49. What are some ways in which the radial nerve may be injured intraoperatively?
50. How does injury to the radial nerve manifest clinically?
51. What are some ways in which the median nerve may be injured intraoperatively?
52. How does injury to the median nerve manifest clinically?
53. What are some ways in which the sciatic nerve may be injured intraoperatively?
54. How does injury to the sciatic nerve manifest clinically?
55. Which peripheral nerve of the lower extremity is most likely to manifest a postoperative neuropathy?
56. What are some ways in which the common peroneal nerve may be injured intraoperatively?
57. How does injury to the common peroneal nerve manifest clinically?
58. What are some ways in which the anterior tibial nerve may be injured intraoperatively?
59. How does injury to the anterior tibial nerve manifest clinically?
60. What are some ways in which the femoral nerve may be injured intraoperatively?
61. How does injury to the femoral nerve manifest clinically?
62. What are some ways in which the saphenous nerve may be injured intraoperatively?
63. What are some ways in which the obturator nerve may be injured intraoperatively?
64. How does injury to the obturator nerve manifest clinically?
65. Can the intraoperative use of a tourniquet result in nerve injury?
Answers*
1. The position the patient is placed in intraoperatively while under general anesthesia is the responsibility of the anesthesiologist, surgeon, and nurses. The responsibility is shared among these operating room personnel. During the course of surgery the responsibility becomes primarily that of the anesthesiologist, who must be aware of any changes in the patient’s position. (300)
2. An awake patient will typically respond to pain, numbness, or tingling associated with nerve injury. However, positions that would not be tolerated by an awake patient can be assumed for hours while under anesthesia care, especially when combined with drug-induced skeletal muscle relaxation. Therefore, the anesthesiologist must share responsibility for the proper positioning of the patient during anesthesia, for appropriate padding of the pressure points, and must be aware of potential injuries associated with various positions. A description of the positioning and padding should also be documented in the anesthesia record. (300)
3. Potential injuries to the patient that can be sustained during mask ventilation of the airway include damage to the facial nerve and necrosis to the bridge of the nose. Facial nerve injury can be caused by the face strap on the anesthetic mask compressing the buccal branch of the nerve or by the anesthesiologist’s fingers on the ascending ramus of the patient’s mandible. Both of these risks are rare, however.
4. Skin that is subject to excessive or prolonged pressure is at risk for ischemic damage. Areas of skin that are especially prone to ischemic damage during surgery include the heels, supraorbital ridge, and the skin at the corner of the mouth in contact with the endotracheal tube. The risk of skin ischemia can be minimized with adequate padding at potential pressure points.
Specific positions
5. Placement of a patient in the supine position may modestly increase cardiac output secondary to an increase in venous return. This causes a slight, reflex mediated decrease in heart rate that results in minimal changes to the blood pressure. (301)
6. The supine position produces a relatively even distribution of blood flow throughout the lung. (301)
7. The functional residual capacity decreases when a patient’s position is changed from standing to supine, largely because of cephalad displacement of the diaphragm by the abdominal contents. (301)
8. While undergoing surgery in the supine position, the patient’s legs should be positioned with slight flexion at both the hips and knees. Not only does this facilitate venous drainage from the lower extremities, it also decreases the amount of anterior abdominal wall tension during surgical closure of the abdomen. (303, Figure 19-1)
9. Focal alopecia may result from continued pressure on one area of the scalp. This risk may be minimized by padding and by periodically moving the patient’s head during long procedures if possible. (303)
10. Backache may result from surgery in the supine position because of the loss of the normal lordotic curvature of the lumbar spine that can occur, particularly with skeletal muscle relaxation. (303)
11. One or both arms may be placed in the abducted or adducted (tucked) positions while a patient is in the supine position for surgery. (302-303, Figure 19-1, A and C)
12. When the supine patient’s arms are abducted, they should be placed on well-padded armboards. The arms should be extended less than 90 degrees at the shoulder. Some debate exists regarding the position of the hand when the arm is abducted. It is believed that supination of the forearm may result in greater protection of the ulnar nerve from compression. However, supination of the hand may result in greater stretching of the brachial plexus. In addition, supination of the forearm in awake patients is uncomfortable. An alternative is leaving the forearm in the neutral position. The neutral position is the spontaneous position of an awake, supine patient. (302-303)
13. When the supine patient’s arms are adducted, or tucked in to the patient’s side, care should be taken to avoid placing any portion of the arm or fingers against any metal surfaces or hard edges of the operating table. This can be accomplished by padding the arm circumferentially before securing it. Most often the arms are allowed to remain in the neutral position, with the palms facing the patient’s side. (302-303)
14. Placement of a patient in the head-down position, or Trendelenburg position, for a surgical procedure results in increases in central venous, intracranial, and intraocular pressures. The Trendelenburg position is often used to increase venous return during hypotension, to improve exposure during abdominal and laparoscopic surgery, and during central line placement. (303)
15. Placement of a patient in the head-down position for a surgical procedure results in an increase in pulmonary venous pressure and a decrease in pulmonary compliance and functional residual capacity. This occurs secondary to an increase in central venous pressure and from the cephalad displacement of the abdominal contents against the diaphragm. This may manifest as increased peak inspiratory pressure with mechanical ventilation. (303)
16. Placement of a patient in the head-down position for a surgical procedure results in an increase in the intracranial pressure. (303)
17. Brachial plexus injury can occur when shoulder braces are used to prevent the patient from sliding down the table when in the Trendelenburg position. The injury is due to both direct compression and stretching of the brachial plexus. (313)
18. Placement of a patient in the prone position results in cephalad displacement of the diaphragm because of pressure from the abdominal contents against the operating room table. This can lead to a decrease in the functional residual capacity and impairment of diaphragmatic movement manifesting as increased peak inspiratory pressures with mechanical ventilation. This effect of the prone position may be offset by allowing space for the abdomen and chest to move with minimum pressure during respiration. Examples are special tables such as the Jackson table with support only under bony areas, additions to a standard operating room bed such as the Wilson frame, and firm rolls or bolsters placed under each side from the clavicle to the iliac crest. (307-308, Figure 19-4)
19. Placement of a patient in the prone position may result in compression of the inferior vena cava, leading to impaired venous return to the heart and decreased cardiac output. This effect of the prone position may be offset by techniques that reduce compression of the abdomen, as outlined above. Examples include special tables, frames, and bolsters. (308, Figure 19-4, A)
20. Turning the prone patient’s head laterally can result in jugular venous outflow obstruction, as well as obstruction to vertebral artery blood flow and, rarely, thrombosis. In addition, this position can result in postoperative neck pain, especially in patients with a history of cervical arthritis. The brachial plexus is also stretched on the contralateral side. These potential problems can be avoided by placing the patient’s head neutral in a forward-facing position on a padded rest. The padded rest typically supports the patient’s head around the periphery of the face, leaving the center of the face and eyes without contact with the padding. (308, Figure 19-4, D)
21. A potential problem with placing the prone patient’s head in a neutral forward-facing position, as in a Mayfield headrest, is the risk of compression of the face on the table or padding. This can be especially hazardous with unrecognized movement of the patient during the surgery. Of particular concern is pressure on the globes of the eye, which can result in retinal ischemia and blindness. This potential problem can be minimized by frequently checking the patient’s eyes, nose, and ears during the course of the surgical procedure. (308)
22. While in the prone position the patient’s arms should be positioned such that abduction of the arms at the shoulder is limited to less than 90 degrees. The patient’s arms may be placed at the patient’s sides or above the head. This helps to minimize the risk of injury to the brachial plexus. (308)
23. Venous pooling in the lower extremities while the patient is in the prone position can be offset with the placement of fitted elastic stockings or sequential compression devices. (308)
24. Placement of a patient in the lateral decubitus position can result in significant mismatching of pulmonary ventilation-to-perfusion during mechanical ventilation of the lungs for a number of reasons. First, while in the lateral position the mechanically ventilated patient has relatively better ventilation of the nondependent lung as compared to the dependent lung. The reasons for the dependent lung being ventilated less are secondary to the loss of lung volume from compression by abdominal contents and mediastinal contents. The patient concurrently has better perfusion of the dependent lung, primarily secondary to the effects of gravity. Together, these factors result in greater mismatching of ventilation and perfusion of the lungs during mechanical ventilation in a patient in the lateral decubitus position. Clinically, this may manifest as arterial hypoxemia. (306, Figure 19-3)
25. Placement of a patient in the lateral decubitus position can result in compression of the inferior vena cava from the pressure of a kidney rest. This can lead to a decrease in venous return to the heart. (305-306)
26. In the lateral position, the dependent brachial plexus may be injured should the axilla be compressed sufficiently to compress the brachial plexus. An axillary roll properly placed under the thorax caudal to the axilla supports the patient’s chest and minimizes the risk of compression of the nerves and vessels in the axilla. Arterial or pulse oximetry monitoring of the dependent arm may help detect axillary compression. Alternatively, the radial pulse may be checked periodically to ensure complete compression of the artery has not occurred. (306, Figure 19-3, C)
27. The patient’s head and neck while in the lateral decubitus position should be positioned such that the cervical vertebrae of the neck are in line with the thoracic vertebrae. This can be accomplished by placing the patient’s head on a pillow of the correct height. Insufficient padding under the head of the patient in the lateral decubitus position can result in compression and stretching to the brachial plexus and direct compression to the dependent ear and eye. (305-306)
28. The patient’s legs while in the lateral decubitus position should be positioned such that the dependent leg is flexed at the knee and there is a pillow between the two legs. This helps to minimize stretch of the nerves of the dependent leg and distributes more evenly the weight of the legs, such that discrete pressure points are avoided. Indeed, there have been case reports of arterial insufficiency of the dependent leg of patients undergoing hip arthroplasty in the lateral position. (305-306)
29. The patient’s nondependent arm while in the lateral decubitus position should be supported by a holder or padding above and in front of the patient’s face. Alternatively, the arm may be suspended from a support bar that is well padded. Both positions should limit the extension of the arm to less than 90 degrees at the shoulder. (305-306, Figure 19-3, B)
30. The sitting position is most often used for neurosurgical procedures, especially in the posterior fossa, and for orthopedic surgeries on the shoulder. The advantages of the sitting position for posterior fossa craniotomies are improved surgical exposure and facilitated jugular venous drainage leading to less bleeding. (309, Figure 19-5)
31. Patients placed in the sitting position for a surgical procedure may become hypotensive, especially if hypovolemic. Additionally, patients may have decreases in cardiac output and cerebral perfusion pressures. Hypotension can be avoided by positioning the patient in gradual steps to allow for accommodation, by ensuring adequate hydration, and through the temporary administration of small doses of vasopressors. (309)
32. The principal potential intraoperative complication of positioning a patient in the sitting position for neurosurgery is a venous air embolus. Placing the surgical site above the level of the heart during the procedure facilitates the entrainment of air. Patients undergoing craniotomies are especially at risk, given that veins in the bony cranium do not collapse after being transected. (310)
33. Patients with a large abdominal mass, pregnant, or obese patients are most likely to manifest cardiovascular effects when placed in the lithotomy position for a surgical procedure. These patients are more likely to have obstruction of the inferior vena cava in this position. In addition, the lithotomy position leads to the cephalad displacement of the diaphragm by the abdominal viscera, potentially impairing spontaneous ventilation. (305, Figure 19-2)
34. Patients with a history of low back pain may suffer from exacerbation of their pain after being placed in the lithotomy position for surgery. These patients may benefit from assuming the position themselves when awake and choosing the position that is most comfortable for them. An alternative position for surgery may also be considered. (305)
35. The principal potential intraoperative complication of positioning a patient in the lithotomy position for surgery is peripheral nerve injury. Injury can occur to the sciatic, common peroneal, femoral, saphenous, or obturator nerves in this position. This potential problem can be minimized by ensuring that the patient’s legs are well padded in areas where they could potentially be compressed such as against metal braces. While positioning the patient, the legs should be lifted simultaneously, flexed no more than 90 degrees at the hip, and then simultaneously rotated for placement into the stirrups. (305, Figure 19-2, B and C)
36. Compartment syndrome secondary to inadequate circulation can result from placing a patient in the lithotomy position for more than 4 hours during a surgical procedure. The common initiating event is probably direct local muscle pressure. This can occur from inadequate padding, tight leg straps, or the surgeon leaning on the leg for a prolonged period of time. The direct pressure may lead to arterial insufficiency, tissue necrosis and edema, and rhabdomyolysis. (305)
37. A patient’s digits of the fingers or toes can be injured intraoperatively during moving of operating table parts. Movement of the table into a space where the fingers or toes lie could lead to crushing of the digit. (304-305, Figure 19-2, D)
Peripheral nerve injury
38. Peripheral nerve injuries are responsible for 18% of closed claims in the ASA Closed Claims Project, second only to death (22%). Peripheral nerve injuries have occurred in patients after regional anesthesia, monitored anesthesia care, and general anesthesia. The causes of a peripheral nerve injury are often multifactorial. However, injury occurring to a nerve intraoperatively is felt to be due to ischemia from compression or stretching of the nerve. The injury usually sustained to the nerve is neurapraxic, which is a loss of function without corresponding anatomic injury. The risk of sustaining an intraoperative nerve injury can be minimized by carefully positioning patients and by using padding when and where appropriate. There is evidence to suggest that patients who experience intraoperative nerve injury may have preexisting conditions that made the injury unavoidable, even with proper positioning and padding. (310-311, Tables 19-1 through 19-3)
39. Risk factors for peripheral nerve injury include extreme positions, male sex for ulnar nerve injury, extremes of weight, hypotension, prolonged tourniquet time, and central venous or arterial catheter placements. The prone “superman” and lateral decubitus positions appear to be risk factors for upper extremity nerve injuries. (312-313)
40. The usual recovery time from an intraoperative peripheral nerve injury is 3 to 12 months. In rare cases, injury can be permanent, particularly with a stretch injury that results in disrupted axons. (315)
41. The most common peripheral nerve to manifest a postoperative neuropathy is the ulnar nerve. The mechanism of ulnar neuropathy is felt to be multifactorial and remains poorly understood, å and therefore is not completely preventable. (311-313)
42. The ulnar nerve may be injured intraoperatively secondary to compression of the nerve against the posterior aspect of the medial epicondyle of the humerus or in the cubital tunnel. There also appears to be an increased incidence of ulnar nerve injury associated with sternal retraction during cardiac surgery. The ulnar nerve may be at a greater risk of injury when the elbow is hyperflexed or the forearm is pronated. Supination of the forearm intraoperatively may provide some protection to the ulnar nerve, although this may increase the risk to the brachial plexus. (311-313)
43. Males are five times more likely to acquire an ulnar neuropathy than females, possibly due to anatomic differences. (313)
44. Ulnar nerve injury manifests clinically as decreased sensation over the ventral and dorsal portions of the medial 1½ fingers, and an inability to abduct or oppose the fifth finger. Over time, ulnar nerve injury results in the appearance of a “claw hand” secondary to atrophy of the intrinsic muscles. (311-313)
45. The second most common peripheral nerve injured during surgery is the brachial plexus. (310)
46. The brachial plexus is especially susceptible to nerve injury during surgery because its course is superficial and fixed between two points: the vertebra and the axillary fascia. In addition, it lies close to the clavicle and humerus, which are very mobile, and slings under the clavicle and the pectoralis muscles. (313)
47. The brachial plexus may be injured intraoperatively through both stretching and compression of the plexus. Stretching of the brachial plexus can occur with neck extension, with turning the head to the opposite side, or with the patient in the lateral decubitus position with inadequate padding to support the neck in the midline position. It can also occur in any position when the arm is abducted more than 90 degrees. Compression of the brachial plexus may occur with inappropriately placed shoulder braces or during spreading of the sternum during cardiac surgery. (313)
48. Injury to the brachial plexus manifests as a limply hanging arm at the side, rotated medially, with a pronated forearm. This position of the arm is commonly referred to as “waiter’s tip.” (313)
49. The radial nerve may be injured intraoperatively if the arm slips off the surgical table or if pressure is applied to the humerus where the radial nerve runs in the spiral groove. A rare cause of radial nerve injury is the mechanical effects of an automated blood pressure cuff. (313)
50. Injury to the radial nerve manifests as decreased sensation over the dorsal surface of the lateral three fingers and an inability to extend the metacarpophalangeal joints or abduct the thumb. It is also characterized by wristdrop. (313)
51. The median nerve may be injured intraoperatively by the insertion of an intravenous catheter into the antecubital fossa or by the extravasation of injected medications. (313)
52. Injury to the median nerve manifests as decreased sensation on the palmar surface of the lateral three fingers and an inability to oppose the first and fifth digits. (313)
53. The sciatic nerve may be injured intraoperatively by direct compression of the nerve or during intramuscular injections in the upper, outer quadrant of the buttocks. Injury may also occur by stretching with external rotation of the leg, which most often occurs while in the lithotomy position. The risk of sciatic nerve stretching can be minimized by the avoidance of excessive rotation of the legs at the hip while in the lithotomy position. Injury of the sciatic nerve may be mistaken as injury to the peroneal nerve, because the peroneal nerve is a branch of the sciatic nerve. (313-314)
54. Injury to the sciatic nerve manifests as decreased sensation over the lateral leg and foot, and weakness of all the skeletal muscles below the knee. (313-314)
55. The most common peripheral nerve in the lower extremity to manifest a postoperative neuropathy is the common peroneal nerve. (313-314)
56. The common peroneal nerve may be injured intraoperatively by compression between the patient’s fibula and leg support for the lithotomy position. The risk of this nerve injury can be minimized with appropriate padding, limiting the length of cradle leg rests to avoid pressure on the fibular head, and strict attention to candy cane leg holders to avoid contact with the leg. (313-314)
57. Injury to the common peroneal nerve manifests as a loss of dorsal extension of the toes, inability to evert the foot, and footdrop. (313-314)
58. The anterior tibial nerve may be injured intraoperatively with prolonged plantar flexion of the feet. This risk can be avoided by placing a roll under the ankles of patients in the prone position.
59. Injury to the anterior tibial nerve manifests as footdrop.
60. The femoral nerve may be injured intraoperatively by compression from a pelvic retractor against the pelvic brim during abdominal surgery. It may also occur with excessive flexing and external rotation at the groin while in the lithotomy position. (314)
61. Injury to the femoral nerve manifests as a decreased sensation over the superior aspect of the thigh, as well as on the medial and anteromedial side of the leg. (314)
62. The saphenous nerve may be injured intraoperatively by compression against the medial tibial condyle and a metal support for the lithotomy position when the brace is placed medial to the patient’s leg. The risk of a saphenous nerve injury may be minimized with the appropriate use of padding.
63. The obturator nerve may be injured intraoperatively during a difficult forceps-assisted vaginal delivery or by excessive flexion of the thigh to the abdomen, as during vaginal delivery.
64. Injury to the obturator nerve manifests as decreased sensation over the medial thigh and an inability to adduct the leg.
65. The intraoperative use of a tourniquet can result in nerve injury, particularly if the inflation time of the tourniquet exceeds 2 hours or with the application of excessive tourniquet pressures. For this reason, after about 2 hours if there is a continued need for the tourniquet, it may be prudent to deflate it for 15 minutes and reinflate it. (314)
Perioperative eye injury and visual loss
66. Although quite rare, eye complications accounted for 3% of all claims (ASA Closed Claims Project Database) and were associated with greater monetary settlements as compared with nonocular injuries. Corneal abrasion continues to be the most common type of perioperative eye injury. (314)
67. Postoperative visual loss is a rare devastating complication associated with patients undergoing spine surgery in the prone position and in cardiac surgery with cardiopulmonary bypass. Ischemic optic neuropathy (ION) and to a lesser extent central retinal arterial occlusion (CRAO) from direct eye compression are the conditions most commonly cited as potential causes. (314)
68. The causes of postoperative visual loss appear to be multifactorial in nature. However, patient risk factors include hypertension, diabetes, atherosclerosis, morbid obesity, and smoking. Perioperative risk factors for patients undergoing spine surgery in the prone position include prolonged hypotension, long duration of surgery, large volumes of blood loss, large crystalloid use, anemia or hemodilution, and increased intraocular or venous pressure. (314)
69. The ASA Committee on Professional Liability established the ASA Postoperative Visual Loss (POVL) registry to study the complication. By 2005, 131 cases were reported to the registry of which 73% of the cases occurred during spine surgeries and 9% involved cardiac surgery. Of patients with POVL undergoing spine surgery, 89% of patients were diagnosed with ION, predominantly posterior, and 11% with CRAO. (314)
Evaluation and treatment of perioperative neuropathies
70. Neurologic consultation obtained early after a peripheral nerve injury manifests in the postoperative period may be useful in detecting between acute and chronic injury. This can be accomplished through nerve conduction velocity and electromyographic studies. Signs of denervation from acute nerve injury are detected by an electromyogram 18 to 21 days after the injury, emphasizing the importance of obtaining neurologic consultation before this time. It may also be useful to test the same nerve in the limb opposite the symptomatic one to exclude any preexisting nerve injury that is asymptomatic. When the injury is reversible, recovery often takes place within 3 to 12 months. (315)
