Nerve Flashcards
What is the optimal surgical intervention to restore elbow flexion in an upper brachial plexus palsy primarily involving C5/C6 with partial C7 weakness, 9-months post-injury?
Median and ulnar nerve double fascicular nerve transfer.
Why are exploration and nerve grafting or allografting not optimal at 9 months post-injury for restoration of elbow flexion in a brachial plexus injury involving C5/C6 roots?
Axon regeneration across grafts at this stage would further delay reinnervation and muscle recovery by an additional 9-12 months, significantly reducing functional outcomes.
In a double fascicular nerve transfer to restore elbow flexion, which donor fascicles are typically used?
An ulnar nerve fascicle from the FCU to the biceps and a median nerve fascicle from the FCR to the brachialis.
Following a PIN palsy, after recovery of the Extensor Digitorum Communis (EDC), which muscles typically recover next?
Extensor Carpi Ulnaris (ECU), centralizing wrist extension.
In recovery from PIN palsy, which muscle typically recovers last?
Extensor Indicis Proprius (EIP).
What is a clinical sign indicating ECU reinnervation during recovery from a PIN palsy?
Wrist extension becomes centralized rather than radially deviated.
After a complete median nerve division at wrist level, which muscle typically remains functional due to dual innervation?
Flexor Pollicis Brevis (FPB).
What anatomical variant explains persistent FPB function following median nerve division at the wrist?
Riché-Cannieu anastomosis.
Which thenar muscle reliably indicates exclusive median nerve innervation and would thus be dysfunctional following median nerve division at the wrist?
Abductor Pollicis Brevis (APB).
Which medical treatment for Carpal Tunnel Syndrome has documented neurophysiological improvement?
Corticosteroid infiltration of the carpal tunnel.
Does wrist splinting in 30° extension optimize the carpal tunnel volume for Carpal Tunnel Syndrome treatment?
No, wrist splinting in neutral provides the greatest tunnel volume.
Which vitamin is commonly implicated in peripheral neuropathy relief but lacks evidence in carpal tunnel syndrome treatment?
Vitamin B6 (Pyridoxine).
What does Wartenberg’s sign indicate in hand examination?
Paralysis of the 3rd palmar interosseous muscle due to ulnar nerve palsy.
Why is the little finger abducted in Wartenberg’s sign?
Unopposed radial nerve innervation of extensor digiti minimi due to paralysis of the ulnar-innervated palmar interossei.
Which muscle recovers earlier during regeneration following ulnar nerve injury, potentially increasing Wartenberg’s sign?
Abductor digiti minimi (ADM).
How does demyelination affect nerve conduction studies?
Reduces conduction velocity.
What does axonal loss primarily affect in nerve conduction studies?
Reduction of Compound Motor Action Potential (CMAP) amplitude.
What physiological phenomenon do F-waves represent in nerve conduction studies?
Propagation of impulses proximally to anterior horn cells and back.
Which principle is NOT critical for successful tendon transfer surgery?
Strength of at least MRC grade 3 in donor musculotendinous unit.
Why must the donor tendon have synergistic function in tendon transfers?
To maintain natural and effective motion post-transfer.
What must be ensured regarding soft tissues during tendon transfer surgery?
Healthy, inflammation-free soft tissues without significant scarring or edema.
What length of sural nerve graft is typically harvestable from a single leg?
30-40 cm.
Which autologous nerve graft is vascularized by the superior ulnar collateral artery (SUCA)?
Vascularized ulnar nerve graft.
Compared to medial antebrachial cutaneous nerve, how much longer is the lateral antebrachial cutaneous nerve graft?
More than double in length.
In chronic recurrent cubital tunnel syndrome with intrinsic muscle wasting and no motor potentials on EMG, which procedure is NOT appropriate?
Revision cubital tunnel release and anterior interosseous nerve (AIN) transfer.
What operative interventions are reasonable in chronic recurrent cubital tunnel syndrome to relieve pain, even with advanced muscle wasting?
Revision cubital tunnel release combined with medial epicondylectomy or anterior transposition, possibly with nerve wrapping.
Why is anterior interosseous nerve (AIN) transfer contraindicated in late-stage recurrent cubital tunnel syndrome with extensive intrinsic wasting?
Muscle end-plates have degenerated, and muscles are no longer amenable to reinnervation.
How does shoulder shrugging affect thoracic outlet compression?
Widens the space between clavicle and first rib, reducing compression.
Where is the phrenic nerve typically identified during thoracic outlet syndrome surgery?
On the surface of scalenus anterior muscle, passing lateral-proximal to medial-distal.
What characterizes a ‘post-fixed’ brachial plexus in thoracic outlet syndrome?
A large T2 contribution and minor or absent C5 root.
In a patient with a symptomatic superficial radial nerve neuroma-in-continuity who desires preservation of distal sensation, what is the optimal method for reconstructing an 18mm nerve gap after resection?
Processed nerve allograft reconstruction.
Why is conduit reconstruction not the best option for an 18mm nerve gap following neuroma resection?
Conduits are most effective for nerve gaps smaller than 6mm.
Why should proximal implantation or capping of the nerve stump not be the first-line option in treating a superficial radial nerve neuroma with preserved distal sensation?
Both techniques eliminate distal sensation, which the patient explicitly wishes to preserve.
What is the leading global cause of spinal cord injury?
Motor vehicle accidents.
In tetraplegia, why must the function of the biceps, brachialis, and supinator be assessed before tendon transfer surgery?
Because these muscles share innervation from C5/C6 and ensure preserved elbow flexion and supination function necessary for successful tendon transfer, especially the biceps-to-triceps procedure.
Is nerve function below the injured spinal cord level always completely absent in tetraplegic patients?
No, nerve function below the lesion can still potentially be stimulated and re-innervated via nerve transfers if the lower motor neuron unit remains intact.
Does the superficial radial nerve run superficially proximal or distal to the radio carpal joint?
It becomes superficial approximately 7 cm proximal to the radio carpal joint.
Which radial nerve branch commonly innervates the extensor carpi radialis brevis (ECRB) muscle?
The superficial branch of the radial nerve can often innervate the ECRB muscle.
Injury to which nerve typically presents with wrist drop?
Posterior interosseous nerve (branch of the radial nerve).
In Parsonage-Turner syndrome presenting with persistent weakness and positive Tinel’s signs at the proximal forearm and carpal tunnel, what is the recommended management?
Proximal median nerve and carpal tunnel decompression.
Why is conservative management inappropriate when Parsonage-Turner syndrome recovery has plateaued and Tinel’s signs are advancing?
Conservative management would miss the critical window for surgical decompression, potentially compromising further recovery once nerve regeneration is stalled.
Why are corticosteroids and antivirals not effective 9 months into Parsonage-Turner syndrome?
Such treatments are beneficial only during acute neuritis phases, not in late-stage or chronic presentations where inflammation has resolved.
What tendon transfer is best for restoring thumb opposition in a patient with incomplete median nerve motor recovery?
Extensor indicis proprius opponensplasty (Burkhalter).
Why would a Camitz transfer (palmaris longus) be inappropriate in an adult patient with median nerve injury?
The palmaris longus is typically involved in scarring from initial injury or repair, limiting excursion and transfer effectiveness.
In cases of combined median nerve injury and cubital tunnel syndrome, why is opponensplasty indicated concurrently with cubital tunnel release?
Concurrent procedures simultaneously address thumb opposition deficits and ulnar nerve symptoms, optimizing functional hand recovery.
Which muscle is directly innervated by the axillary nerve?
Teres minor muscle.
Is the teres major muscle innervated by the axillary nerve?
No, it receives innervation from the lower subscapular nerve.
What nerve innervates the medial head of the triceps brachii?
Radial nerve.
In the International Classification for Tetraplegia Hand Surgery, a patient with intact ECRL/ECRB but weak pronation falls under which group?
Group 3.
Which muscle presence differentiates group 2 from group 3 in the tetraplegic hand surgery classification?
The presence of extensor carpi radialis brevis (ECRB) differentiates group 3 (with ECRB) from group 2 (without ECRB).
Would a patient with grade 4 wrist flexion be classified as group 3 or group 5?
Group 5.
What histological pattern is typical of traumatic neuroma?
Extensive microfascicle formation with haphazard arrangement, unmyelinated fascicles, and dense fibrous tissue without encapsulation.
Are microfascicles in traumatic neuromas typically encapsulated?
No, traumatic neuromas are typically unencapsulated, involved with dense scar tissue.
What cells are prominent in traumatic neuromas?
Schwann cells, axons, and surrounding perineurium.
Can a single gracilis muscle transfer simultaneously restore elbow flexion and finger extension?
Yes, by transferring a single gracilis with appropriate tendon lengthening and fascial grafting for both movements.
Is gracilis muscle transfer affected negatively by a non-functioning antagonist muscle?
Yes, antagonist function significantly affects functional outcomes.
Is the gracilis muscle a Type 1 or Type 2 muscle according to Mathes and Nahai?
Type 2, having one dominant and one minor vascular pedicle.
Which muscles are commonly innervated by the recurrent motor branch of the median nerve?
Opponens pollicis, abductor pollicis brevis, and superficial part of the flexor pollicis brevis.
Does the recurrent median nerve branch typically innervate lumbricals or interossei muscles?
No, lumbricals (index and middle finger) are supplied by median nerve digital branches, and interossei are innervated exclusively by the ulnar nerve.
Which part of the flexor pollicis brevis muscle is typically innervated by the recurrent median nerve?
The superficial part.
Is endoscopic carpal tunnel release as effective as open carpal tunnel decompression?
Yes, endoscopic carpal tunnel release is at least as effective as open decompression in terms of symptom relief, neurophysiology improvement, and patient satisfaction.
What is the approximate conversion rate from endoscopic to open carpal tunnel release?
Approximately 2.5%, significantly lower than the suggested 20%.
What is the most common complication associated with endoscopic carpal tunnel release?
Neurapraxia of the third common digital nerve.
This complication occurs more frequently than injury to the palmar cutaneous branch of the median nerve.
Which extracellular molecule positively guides regenerating axons after nerve injury?
Laminin.
Laminin and fibronectin are glycoproteins promoting axonal elongation and providing positive guidance cues.
Do semaphorins and ephrins provide positive or negative guidance to regenerating axons?
Negative (repulsive) guidance.
They establish exclusion zones preventing aberrant axonal growth.
Why are both positive and negative guidance cues important in axonal regeneration?
They collectively guide regenerating axons along appropriate pathways by attraction and repulsion mechanisms, ensuring correct axonal targeting.
Which type of nerve injury typically results in the worst outcomes after surgical repair?
Closed traction injuries with extensive intraneural damage and concomitant vascular injury.
Severe ischemia, wide retraction, and extensive fibrosis greatly impair recovery.
Why do sharp nerve lacerations typically have better outcomes compared to blunt or traction injuries?
Sharp lacerations create a narrow zone of injury with minimal adjacent tissue trauma, facilitating more effective surgical repair and regeneration.
How does the presence of concomitant arterial injury influence nerve repair outcomes?
It worsens prognosis due to additional ischemic damage, complicating nerve regeneration and increasing scarring.
What is a common trophic change associated with Complex Regional Pain Syndrome (CRPS)?
Osteopenia, along with hair, skin, and nail atrophy.
Does CRPS exhibit a clear dermatomal or peripheral nerve distribution pattern?
No, CRPS typically lacks a clear dermatomal or peripheral nerve distribution pattern, differentiating it from specific nerve injuries.
What differentiates CRPS Type 1 from Type 2?
Type 2 involves a definite peripheral nerve injury, while Type 1 does not.
At 3 months post-ulnar shaft fracture fixation, what EMG findings indicate surgical nerve exploration?
Fibrillation potentials and positive sharp waves indicating denervation, combined with absent motor unit potentials.
Why are nascent motor unit potentials on EMG not a reliable indication for urgent surgical exploration?
They suggest early reinnervation and collateral sprouting rather than ongoing axonal injury requiring surgical intervention.
Does muscle wasting of intrinsic hand muscles alone justify urgent surgical exploration at 3 months post-injury?
No, intrinsic muscle wasting at this stage typically reflects previous axonal loss, not ongoing injury requiring immediate exploration.
Which test has the highest sensitivity and specificity for diagnosing carpal tunnel syndrome?
Durkan’s Test (carpal tunnel compression test) has greater sensitivity and specificity than Phalen’s or Tinel’s tests.
Which test involves assessing the radial pulse with the patient’s head rotated and extended?
Adson’s Test, used in diagnosing thoracic outlet syndrome by noting diminished radial pulse indicating vasogenic symptoms.
Which sign indicates ulnar nerve dysfunction in the intrinsic hand muscles?
Pitres-Testut sign, characterized by inability to abduct the middle finger radially or ulnarly due to ulnar intrinsic dysfunction.
Which test can differentiate between rupture or avulsion of a brachial plexus nerve root?
Tinel’s Sign at Erb’s point helps differentiate rupture (positive Tinel’s sign) from avulsion (negative Tinel’s).
Which maneuver evaluates the suitability for anti-claw procedures?
Bouvier maneuver, assessing ability to extend IP joints with MCP joints flexed.
What anatomical structure commonly compresses the posterior interosseous nerve?
Arcade of Frohse, a fibrous arch from the supinator muscle.
Which anatomical variant transfers motor fibers from the median nerve to the ulnar nerve?
Martin-Gruber anastomosis.
Which ligament can cause ulnar nerve compression in Guyon’s canal?
Superficial Piso-Hamate ligament.
What anomaly tethers the median nerve in the distal forearm?
Linburg-Comstock anomaly, an abnormal connection between FPL and FDP of the index finger.
Which anatomical branch connects median and ulnar sensory territories in the palm?
Berrettini branch, providing sensory communication between these nerves.
Which receptor type is slow-adapting, not encapsulated, and responds to static touch?
Merkel cell neurite complex (Merkel discs).
Which receptor rapidly adapts, has a large receptive field, and senses deep pressure and fast vibration?
Pacinian corpuscles.
Which receptor is encapsulated, slow-adapting, and responds to static touch and stretch?
Ruffini end-organs.
Which receptor rapidly adapts, has a small receptive field, and senses moving touch with slow vibration?
Meissner corpuscles.
Which receptor type, not encapsulated, senses pain and temperature?
Free nerve endings.
Which neuroma treatment involves wrapping nerve stumps in a free muscle graft?
Regenerative peripheral nerve interface.
Which neuroma management technique deliberately sacrifices sensory function in two nerve territories?
Centro-central anastomosis, resulting in sensory deficit in both donor nerves.
Preferred reconstruction for neuroma-in-continuity with preserved distal function?
Autograft/allograft reconstruction.
Which technique involves significant size mismatch during neurorrhaphy?
Targeted Muscle Reinnervation (TMR), often matching large sensory nerves to smaller motor branches.
Neuroma management with the highest recurrence of symptoms?
Relocation nerve grafting (“graft to nowhere”).
Optimal nerve donor to restore deltoid function after C5 nerve root avulsion?
Triceps branch transfer to the axillary nerve (Leechavengvongs procedure).
Best nerve transfer to restore supraspinatus function in C5 avulsion injuries?
Transfer fascicles from the posterior division of C7 to suprascapular nerve.
Recommended nerve transfer to restore spinal accessory nerve function after proximal injury?
Posterior approach spinal accessory medial branch transfer.
Which nerve transfer is indicated to restore finger extension after C8/T1 avulsion?
Supinator branch (C5/C6) to posterior interosseous nerve (PIN) distal to Arcade of Frohse.
Which nerve transfer technique improves ulnar intrinsic muscle function after proximal ulnar nerve repair?
Distal anterior interosseous nerve (AIN) to motor fascicles of the ulnar nerve for early reinnervation of intrinsics.
