Neurapraxic Injury Research Articles

Electrophysiological investigation of motor axonal excitability in a mouse model of nerve constriction injury.

Peripheral nerve injuries caused by focal constriction are characterised by local nerve ischaemia, axonal degeneration, demyelination, and neuroinflammation. The aim of this study was to understand temporal changes in the excitability properties of injured motor axons in a mouse model of nerve constriction injury (NCI). The excitability of motor axons following unilateral sciatic NCI was studied in male C57BL/6J mice distal to the site of injury at the acute (6 hours-1 week) and chronic (up to 20 weeks) phases of injury, using threshold tracking. Multiple measures of nerve excitability, including strength-duration properties, threshold electrotonus, current-threshold relationship, and recovery cycle were examined using the automated nerve excitability protocol (TRONDNF). Acutely, injured motor axons developed a pattern of excitability characteristic of ischemic depolarisation. In most cases, the sciatic nerve became transiently inexcitable. When a liminal compound muscle action potential could again be recorded, it had an increase in threshold and latency, compared to both pre-injury baseline and sham-injured groups. These axons showed a greater threshold change in response to hyperpolarising threshold electrotonus and a significant upward shift in the recovery cycle. Mathematical modelling suggested that the changes seen in chronically injured axons involve shortened internodes, reduced myelination, and exposed juxtaparanodal fast K+ conductances. The findings of this study demonstrate long-term changes in motor excitability following NCI (involving alterations in axonal properties and ion channel activity) and are important for understanding the mechanisms of neurapraxic injuries and traumatic mononeuropathies.

Rapid-stretch injury to peripheral nerves: implications from an animal model.

Rapid-stretch nerve injuries are among the most devastating lesions to peripheral nerves, yielding unsatisfactory functional outcomes. No animal model has yet been developed that uses only stretch injury for investigation of the pathophysiology of clinical traction injuries. The authors' objective was to define the behavioral and histopathological recovery after graded rapid-stretch nerve injury. Four groups of male B6.Cg-Tg(Thy1-YFP)HJrs/J mice were tested: sham injury (n = 11); stretch within elastic limits (elastic group, n = 14); stretch beyond elastic limits but before nerve rupture (inelastic group, n = 14); and stretch-ruptured nerves placed in continuity (rupture group, n = 16). Mice were injured at 8 weeks of age, comparable with human late adolescence. Behavioral outcomes were assessed using the sciatic functional index (SFI), tapered-beam dexterity, Von Frey monofilament testing, and the Hargreaves method. Nerve regeneration outcomes were assessed by wet muscle weight and detailed nerve histology after 48 days. Post hoc biomechanical assessment of strain and deformation confirmed that the differences between the elastic and inelastic cohorts were statistically significant. After elastic injury, there was a temporary increase in foot faults on the tapered beam (p < 0.01) and mild reduction in monofilament sensitivity, but no meaningful change in SFI, muscle weight, or nerve histology. For inelastic injuries, there was a profound and maintained decrease in SFI (p < 0.001), but recovery of impairment was observed in tapered-beam and monofilament testing by days 15 and 9, respectively. Histologically, axon counts were reduced (p = 0.04), muscle atrophy was present (p < 0.01), and there was moderate neuroma formation on trichrome and immunofluorescent imaging. Stretch-ruptured nerves healed in continuity but without evidence of regeneration. Substantial and continuous impairment was observed in SFI (p < 0.001), tapered beam (p < 0.01), and monofilament (p < 0.01 until day 48). Axon counts (p < 0.001) and muscle weight (p < 0.0001) were significantly reduced, with little evidence of axonal or myelin regeneration concurrent with neuroma formation on immunofluorescent imaging. The 3 biomechanical grades of rapid-stretch nerve injuries displayed consistent and distinct behavioral and histopathological outcomes. Stretch within elastic limits resembled neurapraxic injuries, whereas injuries beyond elastic limits demonstrated axonotmesis coupled with impoverished regeneration and recovery. Rupture injuries uniquely failed to regenerate, despite physical continuity of the nerve. This is the first experimental evidence to correlate stretch severity with functional and histological outcomes. Future studies should focus on the pathophysiological mechanisms that reduce regenerative capacity after stretch injury.

Exposure of the brachial plexus in complex revisions to reverse total shoulder arthroplasty.

Excision of extensive scar tissue (EEST) may be required in certain cases of revision reverse total shoulder arthroplasty (RTSA). Neurovascular structures are at a higher risk of iatrogenic direct injury in these cases. We describe a technique to expose and protect the musculocutaneous and axillary nerves in a series of revision RTSA cases that required EEST. Between 2004 and 2013, 83 revision RTSA procedures were identified in our database. Of these, 18 cases (22%) who underwent concomitant nerve exploration for EEST preventing glenoid exposure, preventing reduction of the humeral component, or causing instability of the implanted RTSA, were included. All patients were observed for a minimum of twoyears or until reoperation. Patient-reported outcome scores (PROMs), range of motion (ROM), and complication rates were analyzed. Patients had significant pain relief and improvement in PROMs post-operatively. Two patients (11%) required another revision surgery because of infection (one patient with glenoid loosening; one patient with stem loosening). Two patients (11%) had instability successfully managed with closed reduction. Two patients (11%) had a clinically evident post-operative nerve injury. Both cases were neurapraxias (1 partial brachial plexopathy and 1 partial isolated axillary nerve injury) and experienced complete neurologic recovery at last follow-up. Complete permanent nerve injuries resulting from direct surgical trauma during revision RTSA requiring EEST can be avoided using the technique presented here. Despite proper exposition of the nerves, partial temporary neurapraxic injuries may occur. Patients who underwent this procedure experienced significant improvements in shoulder pain and function with complication rates consistent to those previously reported in revision RTSA.

Iatrogenic nerve injuries in orthopaedics

Peripheral nerves are at risk of injury during both orthopaedic trauma and elective surgery. The aims of this review are to raise awareness of iatrogenic nerve injuries and recommend strategies clinicians can employ to aid diagnosis, management and improve recovery for patients. A thorough understanding of anatomy and appreciation of pathoanatomy in fracture surgery can help reduce this risk. When injuries occur, a systematic clinical assessment can usually locate the site of injury, and with a repeated examination, the physiological grade can be determined. The neurapraxic injury may deteriorate if the conditions around the nerve are unfavourable. Caution should be exerted when making a diagnosis of conduction block because close, regular clinical monitoring is necessary to detect any deterioration early. Surgery may be required in such injuries if there is a failure to progress or deterioration occurs. Higher grade injuries may require surgical exploration and reconstruction. These procedures are most appropriately performed by specialist surgeons working in regional nerve injury units. Early diagnosis and management of an iatrogenic injury reduces the emotional impact, may prevent central pain sensitisation and ensures the optimum chance of useful functional recovery.

Role of Ultrasonography in Evaluation of Peripheral Nerves

Ultrasonography is first line, cost-effective modality in imaging of peripheral nerves. High frequency probes allow high resolution imaging of peripheral nerves located at relatively superficial location. USG can diagnose and localize various pathologies that involve the peripheral nerves such as traumatic, inflammatory, infective, neoplastic, and traumatic neuropathies. USG exceptionally has an important role to play in evaluation of patients with suspected nerve injury, as MRI may not differentiate neural contusion from nerve disruption. Neurapraxic injury is seen as swollen nerve with hypoechoic appearance.

Isolated Traumatic Neurogenic Ptosis With Delayed Recovery

To describe the entity of isolated neurogenic ptosis due to presumed tractional injury to the nerve of innervation of the levator palpebrae superioris, with recovery occurring over a period up to 6 months. Retrospective case review. Three cases of presumed neurapraxic injury to the nerve of innervation to the levator palpebrae superioris are described. Two cases had a clear history of traction to the upper eyelid. There was no evidence of damage to other extraocular muscles or their nerves of innervation in 2 cases and mild transient superior rectus underaction in 1. Maximal recovery occurred over a period of up to 6 months. Traumatic neurapraxic injury to the nerve of innervation to the levator palpebrae superioris may occur in certain types of upper eyelid injury, most notably when there is significant forward traction applied to the upper eyelid. Although recovery may occur within weeks, as previously described, this series illustrates that recovery may take up to 6 months.

Total Hip Arthroplasty with Shortening Subtrochanteric Osteotomy in Crowe Type-IV Developmental Dysplasia

When surgeons perform total hip arthroplasty for hips with a high dislocation related to developmental dysplasia of the hip, obtaining long-term stable implant fixation and optimizing patient function remain challenges. The purpose of this paper was to evaluate the results of cementless arthroplasty with a simultaneous subtrochanteric shortening osteotomy in a group of patients with Crowe type-IV developmental dysplasia of the hip. In a retrospective study, we evaluated the results and complications of twenty-eight consecutive primary cementless total hip arthroplasties in twenty-four patients (twenty women and four men), all of whom had Crowe type-IV developmental dysplasia of the hip. The arthroplasty was performed in combination with a subtrochanteric shortening osteotomy and with placement of the acetabular component at the level of the anatomic hip center. The patients were evaluated at a mean of 4.8 years postoperatively. The mean Harris hip score increased from 43 points preoperatively to 89 points at the time of final follow-up (p < 0.01). Twelve (43%) of the twenty-eight hips had an early or late complication or a reoperation. Two (7%) of the twenty-eight subtrochanteric osteotomies were followed by nonunion. There was one instance of isolated loosening of the femoral stem. One acetabular component loosened, and one acetabular liner disengaged. Four hips dislocated postoperatively. All remaining components were well-fixed at the time of the last radiographic follow-up. No sciatic neurapraxic injuries were identified. Cementless total hip arthroplasty combined with a subtrochanteric femoral shortening osteotomy in patients with a high hip dislocation secondary to developmental dysplasia was associated with high rates of successful fixation of the implants and healing of the osteotomy site and a mean postoperative Harris hip score of 89 points. The complication rate, however, was substantially higher than that associated with primary total hip arthroplasty in patients with degenerative arthritis.

Use of Ultrasound in Detection and Treatment of Nerve Compromise in a Case of Humeral Lengthening

The development of iatrogenic nerve lesions during and following limb lengthening procedures present a challenge to orthopedic surgeons. Early treatment of nerve damage is critical in salvaging full function of the nerve. Precise location of damage, however, must be determined in order to appropriately administer treatment. We report a patient with a short humerus caused by a growth arrest undergoing a 7-cm lengthening who developed a neurapraxic injury of the radial nerve. Nerve compromise was noted 1month into the lengthening program. Nerve conduction studies and electromyography could not be used to determine the precise site of injury. Likewise, magnetic resonance imaging and computed tomography were contraindicated and inconclusive, respectively, due to the presence of a metallic external fixation device. High-resolution ultrasonography (US) findings, however, correlated with our clinical examination of the patient's radial nerve function and permitted identification of the precise site of nerve involvement. Treatment was administered by removing a causative half-pin. Several days following treatment, nerve function returned to normal. There are a limited number of articles in the literature regarding nerve injuries associated with limb lengthening and their corrective treatments. The outcome of this case underscores the usefulness of US over various other diagnostic techniques under certain circumstances.

Total Hip Arthroplasty with Shortening Subtrochanteric Osteotomy in Crowe Type-IV Developmental Dysplasia

When surgeons perform total hip arthroplasty for hips with a high dislocation related to developmental dysplasia of the hip, obtaining long-term stable implant fixation and optimizing patient function remain challenges. The purpose of this paper was to evaluate the results of cementless arthroplasty with a simultaneous subtrochanteric shortening osteotomy in a group of patients with Crowe type-IV developmental dysplasia of the hip. In a retrospective study, we evaluated the results and complications of twenty-eight consecutive primary cementless total hip arthroplasties in twenty-four patients (twenty women and four men), all of whom had Crowe type-IV developmental dysplasia of the hip. The arthroplasty was performed in combination with a subtrochanteric shortening osteotomy and with placement of the acetabular component at the level of the anatomic hip center. The patients were evaluated at a mean of 4.8 years postoperatively. The mean Harris hip score increased from 43 points preoperatively to 89 points at the time of final follow-up (p < 0.01). Twelve (43%) of the twenty-eight hips had an early or late complication or a reoperation. Two (7%) of the twenty-eight subtrochanteric osteotomies were followed by nonunion. There was one instance of isolated loosening of the femoral stem. One acetabular component loosened, and one acetabular liner disengaged. Four hips dislocated postoperatively. All remaining components were well-fixed at the time of the last radiographic follow-up. No sciatic neurapraxic injuries were identified. Cementless total hip arthroplasty combined with a subtrochanteric femoral shortening osteotomy in patients with a high hip dislocation secondary to developmental dysplasia was associated with high rates of successful fixation of the implants and healing of the osteotomy site and a mean postoperative Harris hip score of 89 points. The complication rate, however, was substantially higher than that associated with primary total hip arthroplasty in patients with degenerative arthritis.

Clinics in neurology and neurosurgery of sport: peripheral nerve injury

Peripheral nerve injuries are not uncommon in sports. Typically, these are associated with orthopaedic injury (eg, axillary nerve injury with glenohumeral joint dislocation) rather than the transection or gunshot-type injuries...

Effect of FK506 on Functional Recovery After Facial Nerve Injury in the Rat

To examine the effect of the immunosuppressive agent FK506 on the rate of functional recovery of the rat facial nerve after crush injury. Forty rats underwent facial nerve crush injury and were randomly assigned to 4 experimental groups: isotonic sodium chloride solution control, FK binding protein 52 (FKBP-52) antibody control, FK506, and FK506 and FKBP-52 antibody. Rats underwent daily recovery testing from postoperative day 9 until postoperative day 21 by videotaping 3 validated variables in this model: blink reflex return, vibrissial fibrillation loss, and return of vibrissial sweeping symmetry. FK506-treated animals demonstrated improved recovery in all 3 variables compared with control animals. The FK506 and FKBP-52 antibody group demonstrated improved recovery of only the return of the blink reflex. FK506 accelerated functional recovery of facial nerve function after crush injury. Neuroregeneration was inhibited by FKBP-52 antibody in the rat midface but not the upper face. FK506 may be a viable adjuvant treatment for facial nerve neurapraxic injury.

Comparison of the Vastus-Splitting and Median Parapatellar Approaches for Primary Total Knee Arthroplasty: A Prospective, Randomized Study

A vastus-splitting approach for total knee arthroplasty has been advocated to preserve function of the extensor mechanism and to decrease the prevalence of lateral release. Critics have claimed that there is greater blood loss and compromised exposure in large patients who are managed with this approach. The purpose of the present study was to compare vastus-splitting and median parapatellar approaches for primary total knee arthroplasty. Forty-two consecutive patients (fifty-one knees) undergoing primary total knee arthroplasty were randomized to treatment with a median parapatellar or vastus-splitting approach. The interval of the vastus muscle split was marked with radiopaque vascular clips. Surgical data, functional parameters, and preoperative and postoperative electromyograms were assessed. Early (six-month) and intermediateterm (five-year) follow-up showed no differences in functional parameters, tourniquet time, or the frequency of patellar resurfacing. Significantly more lateral releases (p < 0.01) and greater blood loss (p = 0.03) occurred in the median parapatellar group. Nine (43%) of twenty-one knees in the vastus-splitting group had abnormal electromyographic findings at six months postoperatively, whereas all patients in the median parapatellar group had normal findings. Seven knees with abnormal electromyographic findings at six months had normal findings when restudied at five years; in each of these knees, the vastus split had been developed bluntly. The other two knees with abnormal findings at six months had had sharp dissection for the muscle split. Both of these knees had chronic changes, one with changes indicative of reinnervation and the other with ongoing denervation, but neither demonstrated functional compromise. The vastus-splitting approach offers a viable alternative to the median parapatellar approach for primary total knee arthroplasty that reduces the need for lateral retinacular release without impairment of quadriceps function. Electromyographic abnormalities in the quadriceps muscle have no functional consequence and most likely represent reversible neurapraxic injury that may be avoided by blunt dissection in the vastus medialis muscle.

Ulnar Nerve Palsy Associated With Fracture of the Distal Radius

To describe the clinical features and outcome of a series of patients with complete motor and sensory ulnar nerve palsy associated with a fracture of the distal radius. Retrospective case series. Level 1 trauma center. Five adults with acute complete motor and sensory ulnar nerve palsy associated with fracture of the distal radius were treated during a 2 year period. There were 3 men and 2 women, with an average age of 42 years (range, 33 to 56 years). All 5 distal radius fractures were high energy and widely displaced. Three patients had an associated ulna fracture (2 styloid, 1 styloid and distal diaphysis), and 1 had a complete triangular fibrocartilage complex (TFCC) avulsion from the distal ulna (associated with an open wound). Two patients had open fractures. Open reduction and internal fixation of the distal radius fracture in 4 patients and external fixation in 1 patient. Three patients had exploration and release of the ulnar nerve because it was associated with an acute carpal tunnel syndrome. Recovery of ulnar nerve function. At an average follow-up of 17 months, 4 patients had complete or near-complete recovery of ulnar nerve function. One patient had moderate motor and mild sensory dysfunction. Acute ulnar nerve palsy may occur in association with high-energy, widely displaced fractures of the distal radius. These are usually neurapraxic injuries that recover to normal or near-normal strength and sensation. We recommend exploration and release of a complete ulnar nerve palsy associated with a fracture of the distal radius fracture when there is an open wound or an acute carpal tunnel syndrome, and observation without exploration otherwise.

The insensate foot following severe lower extremity trauma: An indication for amputation?

Conclusion: Insensation of the plantar surface of the foot after lower extremity trauma is not prognostic of long-term plantar sensory status or functional outcome. More than half of patients who presented with an insensate foot after lower extremity trauma ultimately regained sensation at 2 years. Assessment of plantar sensation should not be a component of the limb salvage decision algorithm. Summary: Evaluation of plantar sensation is routine in the assessment of the impact of lower extremity trauma. The authors sought to determine long-term outcome after treatment of severe lower extremity trauma in patients who presented with absent plantar sensation. There were 55 subjects with an insensate extremity at the time of presentation, of whom 26 underwent amputation and 29 were treated for limb salvage. Also included was a control group consisting of patients with lower extremity trauma with intact plantar sensation at presentation who underwent limb reconstruction. Injury characteristics and functional and health-related quality-of-life outcomes at 1 and 2years after injury were compared in the three groups. The insensate salvage group did not have a reported or demonstrated worse outcome at 1 or 2 years compared with the insensate amputation or sensate control groups. Approximately 55% of patients in both the insensate salvage and sensate control groups in whom the limb was salvaged had normal plantar sensation at 2 years after injury. This was regardless of whether plantar sensation had been reported to be intact at the time of presentation after injury. No differences were noted in overall physical or psychosocial scores in the three groups. At 2 years after injury, only one patient in the insensate salvage group had absent plantar sensation. Comment: The data suggest assessment of plantar sensation after lower extremity trauma is essentially worthless in predicting the ultimate sensory status of the foot. These study findings do not support the widespread belief that absent initial plantar sensation in patients with a leg-threatening injury correlates with poor long-term outcome if the limb were to be salvaged. This study implies that tibial nerve dysfunction at the time of presentation does not necessarily imply transaction of the tibial nerve. It is important to remember that reversible ischemic injuries to nerves as well as neurapraxic injuries of peripheral nerves may mimic permanent loss of peripheral nerve function.

The insensate foot following severe lower extremity trauma: An indication for amputation?

Conclusion: Insensation of the plantar surface of the foot after lower extremity trauma is not prognostic of long-term plantar sensory status or functional outcome. More than half of patients who presented with an insensate foot after lower extremity trauma ultimately regained sensation at 2 years. Assessment of plantar sensation should not be a component of the limb salvage decision algorithm. Summary: Evaluation of plantar sensation is routine in the assessment of the impact of lower extremity trauma. The authors sought to determine long-term outcome after treatment of severe lower extremity trauma in patients who presented with absent plantar sensation. There were 55 subjects with an insensate extremity at the time of presentation, of whom 26 underwent amputation and 29 were treated for limb salvage. Also included was a control group consisting of patients with lower extremity trauma with intact plantar sensation at presentation who underwent limb reconstruction. Injury characteristics and functional and health-related quality-of-life outcomes at 1 and 2years after injury were compared in the three groups. The insensate salvage group did not have a reported or demonstrated worse outcome at 1 or 2 years compared with the insensate amputation or sensate control groups. Approximately 55% of patients in both the insensate salvage and sensate control groups in whom the limb was salvaged had normal plantar sensation at 2 years after injury. This was regardless of whether plantar sensation had been reported to be intact at the time of presentation after injury. No differences were noted in overall physical or psychosocial scores in the three groups. At 2 years after injury, only one patient in the insensate salvage group had absent plantar sensation. Comment: The data suggest assessment of plantar sensation after lower extremity trauma is essentially worthless in predicting the ultimate sensory status of the foot. These study findings do not support the widespread belief that absent initial plantar sensation in patients with a leg-threatening injury correlates with poor long-term outcome if the limb were to be salvaged. This study implies that tibial nerve dysfunction at the time of presentation does not necessarily imply transaction of the tibial nerve. It is important to remember that reversible ischemic injuries to nerves as well as neurapraxic injuries of peripheral nerves may mimic permanent loss of peripheral nerve function.

COMPARISON OF THE VASTUS-SPLITTING AND MEDIAN PARAPATELLAR APPROACHES FOR PRIMARY TOTAL KNEE ARTHROPLASTY

Background: A vastus-splitting approach for total knee arthroplasty has been advocated to preserve function of the extensor mechanism and to decrease the prevalence of lateral release. Critics have claimed that there is greater blood loss and compromised exposure in large patients who are managed with this approach. The purpose of the present study was to compare vastus-splitting and median parapatellar approaches for primary total knee arthroplasty. Methods: Forty-two consecutive patients (fifty-one knees) undergoing primary total knee arthroplasty were randomized to treatment with a median parapatellar or vastus-splitting approach. The interval of the vastus muscle split was marked with radiopaque vascular clips. Surgical data, functional parameters, and preoperative and postoperative electromyograms were assessed. Results: Early (six-month) and intermediate-term (five-year) follow-up showed no differences in functional parameters, tourniquet time, or the frequency of patellar resurfacing. Significantly more lateral releases (p < 0.01) and greater blood loss (p = 0.03) occurred in the median parapatellar group. Nine (43%) of twenty-one knees in the vastus-splitting group had abnormal electromyographic findings at six months postoperatively, whereas all patients in the median parapatellar group had normal findings. Seven knees with abnormal electromyographic findings at six months had normal findings when restudied at five years; in each of these knees, the vastus split had been developed bluntly. The other two knees with abnormal findings at six months had had sharp dissection for the muscle split. Both of these knees had chronic changes, one with changes indicative of reinnervation and the other with ongoing denervation, but neither demonstrated functional compromise. Conclusions: The vastus-splitting approach offers a viable alternative to the median parapatellar approach for primary total knee arthroplasty that reduces the need for lateral retinacular release without impairment of quadriceps function. Electromyographic abnormalities in the quadriceps muscle have no functional consequence and most likely represent reversible neurapraxic injury that may be avoided by blunt dissection in the vastus medialis muscle. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Comparison of the Vastus-Splitting and Median Parapatellar Approaches for Primary Total Knee Arthroplasty: A Prospective, Randomized Study

A vastus-splitting approach for total knee arthroplasty has been advocated to preserve function of the extensor mechanism and to decrease the prevalence of lateral release. Critics have claimed that there is greater blood loss and compromised exposure in large patients who are managed with this approach. The purpose of the present study was to compare vastus-splitting and median parapatellar approaches for primary total knee arthroplasty. Forty-two consecutive patients (fifty-one knees) undergoing primary total knee arthroplasty were randomized to treatment with a median parapatellar or vastus-splitting approach. The interval of the vastus muscle split was marked with radiopaque vascular clips. Surgical data, functional parameters, and preoperative and postoperative electromyograms were assessed. Early (six-month) and intermediate-term (five-year) follow-up showed no differences in functional parameters, tourniquet time, or the frequency of patellar resurfacing. Significantly more lateral releases (p < 0.01) and greater blood loss (p = 0.03) occurred in the median parapatellar group. Nine (43%) of twenty-one knees in the vastus-splitting group had abnormal electromyographic findings at six months postoperatively, whereas all patients in the median parapatellar group had normal findings. Seven knees with abnormal electromyographic findings at six months had normal findings when restudied at five years; in each of these knees, the vastus split had been developed bluntly. The other two knees with abnormal findings at six months had had sharp dissection for the muscle split. Both of these knees had chronic changes, one with changes indicative of reinnervation and the other with ongoing denervation, but neither demonstrated functional compromise. The vastus-splitting approach offers a viable alternative to the median parapatellar approach for primary total knee arthroplasty that reduces the need for lateral retinacular release without impairment of quadriceps function. Electromyographic abnormalities in the quadriceps muscle have no functional consequence and most likely represent reversible neurapraxic injury that may be avoided by blunt dissection in the vastus medialis muscle.

Lingual Nerve Injury During Suspension Microlaryngoscopy

Lingual nerve injury is an uncommon complication of laryngoscopy. We report a case of isolated unilateral lingual nerve injury that occurred during suspension microlaryngoscopy. The injury was transient, with complete return of sensation within 3 months after surgery. Several mechanisms have been proposed to explain the occurrence of lingual nerve injury during laryngoscopy, including direct compression of the nerve caused by the laryngoscope, stretching of the nerve caused by cricoid pressure or instrumentation, and compression of the nerve between the medial and lateral pterygoid caused by manipulation of the mandible. The precise mechanism of injury in this case was not obvious, but stretching of the lingual nerve caused by pressure of the suspended laryngoscope on the tongue or retrolingual region was likely. The transient nature of the injury and the rapid return of the nerve to baseline function in this case are consistent with a neurapraxic injury.