01Approach to the Critical Patient/attcp37

Immediate priorities

›Alarm features requiring emergency intervention

›Acute carpal tunnel syndrome (ACTS) with progressive sensory and motor loss after wrist trauma

›Surgical emergency — emergent carpal tunnel release required

›Decompression within 40 hours of symptom onset yields best outcomes

›Normal two-point discrimination achievable in 80% within 96 hours if treated promptly

›Open nerve laceration with visible transection

›Wound care, hemostasis, tetanus prophylaxis

›Primary microsurgical repair ideally within 72 hours

›Forearm compartment syndrome

›Tense volar forearm swelling

›Pain with passive finger extension

›Emergent fasciotomy if confirmed

›Vascular compromise with median nerve injury

›Absent radial pulse, pallor, cold digits

›Combined vascular and nerve repair required

Stabilization and escalation

›Initial stabilization steps

›Wound care and hemostasis for open injuries

›Fracture or dislocation reduction — urgent closed reduction for distal radius fractures and lunate/perilunate dislocations

›Splinting in neutral wrist position (avoid palmar flexion, which increases carpal tunnel pressure)

›Remove constrictive dressings or casts if symptoms worsen

›Tetanus prophylaxis for open wounds

›Escalation triggers

›Progressively worsening pain and sensory loss after wrist trauma — suspect ACTS

›Carpal tunnel pressure >40 mmHg on wick catheter measurement

›Complete loss of two-point discrimination (>15 mm) in median nerve distribution

›Rapidly evolving thenar weakness or paralysis

02History/hx35

Mechanism and onset

›Mechanism of injury

›Laceration (glass, knife, saw)

›Blunt trauma, crush injury

›Fracture (distal radius most common)

›Dislocation (lunate or perilunate)

›Iatrogenic (IV access, surgical positioning, casting in palmar flexion)

›Timing of symptom onset relative to injury

›Immediate onset — suggests nerve contusion or transection

›Progressive worsening after injury — critical distinction for ACTS vs. neurapraxia

›Cotton-Loder position (prolonged wrist flexion) history

Neurologic symptoms

›Sensory distribution

›Numbness and tingling in thumb, index, middle, and radial half of ring finger

›Palmar surface involvement

›Comparison to ulnar territory (dorsal hand and small finger spared in median nerve injury)

›Motor symptoms

›Difficulty with pinch grip

›Inability to oppose thumb to small finger

›Inability to make "OK" sign (anterior interosseous nerve branch — FPL + FDP to index)

›Pain characteristics

›Severity, location, progression

›Worsening pain after reduction or casting — red flag for ACTS

Risk factors and context

›Patient factors

›Hand dominance and occupational demands

›Diabetes mellitus (increases susceptibility and impairs recovery)

›Obesity, hypothyroidism, pregnancy

03Physical Exam/exam30

Neurologic examination

›Sensory testing

›Light touch in median nerve distribution (thumb, index, middle, radial ring finger)

›Two-point discrimination — >15 mm indicates significant sensory loss

›Semmes-Weinstein monofilament testing for quantitative sensory assessment

›Comparison to ulnar territory on same hand

›Motor testing

›Thumb abduction against resistance (abductor pollicis brevis) — most reliable isolated median motor test

›Thumb opposition (opponens pollicis) — ask patient to touch thumb to small finger

›"OK" sign (FPL + FDP to index) — tests anterior interosseous nerve

›Grip strength assessment

›Thenar atrophy — suggests chronic or severe acute denervation

Provocative and vascular tests

›Provocative tests (more relevant in entrapment context)

›Tinel sign over carpal tunnel — 50% sensitivity

›Phalen test (sustained wrist flexion 60 seconds) — 68% sensitivity

›Durkan compression test — 64% sensitivity

›Vascular assessment

›Radial and ulnar pulse palpation

›Allen test for radial or ulnar dominance

›Capillary refill in all digits

Wound and compartment assessment

›Wound inspection

›Laceration depth, contamination, visible structures

›Open fracture involvement

›Foreign body concern

›Compartment assessment

›Forearm firmness (tense swelling suggests compartment syndrome)

04Differential Diagnosis/ddx44

Surgical emergencies

›Acute carpal tunnel syndrome (ACTS)

›ICD-10 G56.0

›Progressive sensory loss after wrist trauma — initially normal sensation that worsens

›Severe pain under cast or splint

›Carpal tunnel pressure >40 mmHg on wick catheter

›Differentiated from neurapraxia by progressive vs. immediate/nonprogressive course

›Forearm compartment syndrome

›ICD-10 T79.A1

›Tense forearm swelling, pain with passive finger extension

›Involves multiple nerves and muscles

›Open nerve transection (neurotmesis)

›ICD-10 S54.1

›Visible laceration, complete immediate sensory and motor loss

›No spontaneous recovery without surgical repair

Nerve injury patterns

›Median nerve neurapraxia

›ICD-10 S54.11

›Immediate, nonprogressive sensory loss after closed injury

›Full recovery expected without surgery

›Anterior interosseous nerve syndrome

›ICD-10 G56.10

›Pure motor deficit — no sensory loss

›Inability to make "OK" sign (FPL + FDP index)

›Pronator syndrome

›ICD-10 G56.10

›Forearm pain with median nerve sensory changes

›Compression at pronator teres

05Laboratory Tests/lt16

Trauma and pre-operative labs

›Standard trauma laboratory panel

›Complete blood count for bleeding concern and baseline

›Basic metabolic panel for electrolyte and renal function status

›Coagulation studies (PT/INR, aPTT) if surgical candidate anticipated

›Type and screen if operative intervention planned

›Metabolic screening

›Glucose and HbA1c — screen for diabetes affecting nerve recovery prognosis

›TSH if hypothyroidism suspected as contributing factor

›Vitamin B12 with methylmalonic acid if concurrent polyneuropathy suspected

›ESR and CRP if inflammatory or infectious etiology considered

Adjunct labs

›Labs generally low yield in isolated acute traumatic median nerve injury

›Prioritize clinical examination and imaging over routine bloodwork

›Targeted workup based on suspected contributing conditions

›Neuropathic pain medication safety labs

›Renal function before gabapentin or pregabalin initiation (dose adjustment required)

›ECG before tricyclic antidepressant initiation — QTc and conduction assessment

06Diagnostic Tests/dt75

Scoring Systems

›Seddon classification for nerve injury severity

›Neurapraxia (Sunderland Grade I)

›Demyelination only, axon intact

›Conduction block at injury site

›Full recovery expected in days to weeks

›Axonotmesis (Sunderland Grades II to III)

›Axonal disruption with preserved connective tissue framework

›Wallerian degeneration occurs distally

›Recovery possible but slow — ~1 mm/day axonal regrowth

›May take months to years for functional recovery

›Neurotmesis (Sunderland Grades IV to V)

›Complete nerve disruption including connective tissue

›No spontaneous recovery

›Requires microsurgical repair

›Functional outcome grading

›Grade 0 — no muscle contraction

›Grade 1 — flicker of contraction

›Grade 2 — movement with gravity eliminated

›Grade 3 — movement against gravity

›Grade 4 — movement against resistance (partial or full)

›Grade 5 — full normal strength

MRI

›MRI neurography indications

›Gold standard for soft tissue detail in peripheral nerve injury

›Indicated for severe weakness or multiple nerve involvement

›Evaluation for space-occupying lesions compressing the nerve

›MRI findings in nerve injury

›Nerve discontinuity — identifies neurotmesis

›Denervation edema in target muscles — high T2 signal

›Increased nerve cross-sectional area at compression point

›Neuroma in continuity — critical for surgical planning

›MRI limitations

›Cost and availability compared to ultrasound

›Longer imaging time

›Claustrophobia or implant contraindications

›Does not replace electrodiagnostic studies for grading

CT

›CT wrist and forearm indications

›Complex fracture characterization

›Intra-articular involvement assessment

›Preoperative planning for comminuted distal radius fractures

›Lunate or perilunate dislocation confirmation and surgical planning

›CT limitations in nerve injury

›Poor soft tissue contrast for direct nerve visualization

›Does not assess nerve continuity or function

›Reserved for bone pathology rather than nerve evaluation

›Plain radiograph (first-line before CT)

›Wrist and forearm X-ray — first-line to evaluate for fracture and dislocation

›Distal radius fracture patterns (Colles, Smith, volar lip)

›Lunate and perilunate dislocation on lateral view

Ultrasound

›Point-of-care ultrasound for median nerve injury

›Assessment of nerve continuity (intact vs. transected)

›Hematoma identification causing extrinsic compression

›Foreign body localization in penetrating trauma

›Neuroma identification and characterization

›Ultrasound quantitative assessment

›Cross-sectional area of median nerve at carpal tunnel inlet

›Normal cross-sectional area <9 to 10 mm squared

›Increased area indicates swelling or compression

›Hypoechoic swelling of nerve at injury site

›Ultrasound advantages

›Dynamic assessment of nerve during wrist movement

›Immediate bedside availability

›No radiation

›Guides aspiration of compressive hematoma

Electrodiagnostic studies

›NCS and EMG — gold standard for diagnosis, severity grading, and prognosis

›Optimally performed 3 to 4 weeks post-injury when Wallerian degeneration complete

›Fibrillation potentials become evident at 3 to 4 weeks

›Serial EMG monitors for reinnervation (nascent motor unit potentials)

›Early studies (within first week) still useful

›Baseline information for conduction block

›Identifies pre-existing lesions

›Serial EMG at 3 to 4 months to assess reinnervation

›Absence of recovery by this point warrants surgical referral

›Intraoperative nerve action potential recording

›Used to guide neurolysis vs. graft repair for closed injuries without recovery

›Presence of NAP across lesion favors neurolysis over resection and graft

07Disposition/dispo23

Admission criteria

›Admit indications

›ACTS requiring emergent carpal tunnel release

›Open nerve laceration requiring microsurgical repair

›Forearm compartment syndrome requiring fasciotomy

›Polytrauma with associated vascular injury

›Progressive neurologic deficit after reduction

›Borderline compartment pressures requiring serial measurement

›Operating room triggers

›Sharp laceration with complete motor and sensory loss

›Open fracture with nerve involvement

›Vascular injury requiring combined repair

Discharge criteria

›Safe discharge criteria

›Stable neurapraxia or contusion with nonprogressive symptoms

›Closed injury with intact vascular status

›Adequate pain control achievable with oral medications

›Reliable follow-up arranged

›Patient understands return precautions

›Follow-up plan on discharge

›48 to 72 hours for re-evaluation after reduction and splinting

›1 to 2 weeks for wound check

›3 to 4 weeks for initial electrodiagnostic studies

›Hand surgery consultation arranged for all complete nerve injuries

›Critical window — nerve reconstruction ideally within 6 months before irreversible motor endplate degeneration

08Treatment/t54

Emergency surgical management

›Acute carpal tunnel syndrome — emergent surgical decompression

›Carpal tunnel release indicated when ACTS diagnosed

›Decompression within 40 hours of symptom onset optimal

›Normal two-point discrimination in 80% of patients within 96 hours if decompressed promptly

›Carpal tunnel pressure >40 mmHg on wick catheter supports surgical indication

›Splinting in neutral position while awaiting surgery

›Avoid palmar flexion which increases carpal tunnel pressure

›Sharp laceration or neurotmesis repair

›Primary microsurgical epineurial repair

›Ideally within 72 hours for optimal outcome

›Tension-free repair is the gold standard

›Nerve gap management

›Nerve autograft (sural nerve most common donor) for gaps requiring bridging

›Bioengineered conduit for gaps <3 cm

›Surgical outcomes (30-year series)

›Neurolysis achieved Grade 3 or higher functional recovery in 95%

›Suture repair achieved recovery in 86 to 91%

›Graft repair achieved recovery in 68 to 75%

›Closed injury without recovery — surgical exploration

›If no clinical or electrophysiologic improvement by 3 to 4 months

›Intraoperative NAP recording guides neurolysis vs. resection and graft

Conservative management

›Neurapraxia and contusion — non-operative approach

›Observation with serial clinical exams

›Splinting in neutral wrist position

›Physical and occupational therapy

›Range of motion maintenance

09Special Populations/sp58

Pregnancy

›Pregnancy-specific considerations

›Carpal tunnel syndrome common in third trimester due to fluid retention and edema

›Median nerve cross-sectional area increased by physiologic edema

›Typically resolves postpartum

›Acute traumatic median nerve injury in pregnancy requires same emergency approach as general population

›Imaging considerations

›Plain X-rays acceptable with appropriate shielding

›MRI preferred over CT for soft tissue assessment

›Ultrasound is safe and preferred for first-line nerve assessment

›Medication safety

›NSAIDs — avoid in third trimester (premature ductus arteriosus closure risk)

›Acetaminophen is preferred first-line analgesic

›Gabapentin and pregabalin — limited safety data in pregnancy; use with caution

›Amitriptyline — weigh risks; limited neonatal effects at low doses

›Surgical considerations

›Carpal tunnel release safe in pregnancy if ACTS develops

›Regional anesthesia preferred over general anesthesia when possible

Geriatric

›Geriatric-specific considerations

›Increased susceptibility to median nerve injury with minor trauma

›Comorbid diabetes, hypothyroidism, and B12 deficiency increase baseline nerve vulnerability

›Pre-existing peripheral neuropathy complicates examination and prognosis

›Distal radius fractures more common in elderly with osteoporosis

›Higher rate of comminution and ACTS risk

›Volar plate fixation increases ACTS risk in this population

›Prolonged immobilization risk

›Functional decline during recovery period

10Background/b52

Epidemiology

›Incidence and prevalence

›Median nerve is the most commonly injured nerve in the upper extremity

›Penetrating trauma (lacerations) is the most common cause of complete nerve transection

›Iatrogenic injury is most common etiology in proximal median nerve injuries — 48.4% of cases

›ACTS occurs in ~4% of distal radius fractures

›Acute median neuropathy occurs in 25% of lunate and perilunate dislocations

›Population and risk distribution

›Distal radius fractures most common in postmenopausal women with osteoporosis

›Penetrating injuries predominant in young males

›Occupational injuries associated with vibration, repetitive use, and power tools

›Hereditary neuropathy with liability to pressure palsies (HNPP) — autosomal dominant condition increasing susceptibility

Pathophysiology

›Anatomy of the median nerve

›Origin — C5 to T1 nerve roots via medial and lateral cords of brachial plexus

›Motor innervation to forearm flexors and thenar muscles (LOAF muscles)

›L — lateral two lumbricals

›O — opponens pollicis

›A — abductor pollicis brevis

›F — flexor pollicis brevis (superficial head)

›Sensory innervation to thumb, index, middle, and radial half of ring finger (palmar surface)

›Anterior interosseous nerve branch — pure motor, FPL, FDP to index, pronator quadratus

›Nerve injury mechanisms

›Wallerian degeneration occurs distal to injury in axonotmesis and neurotmesis

›Begins within hours of injury

›Complete by 7 to 10 days distally

›Explains why EMG unreliable in first week

›Axonal regeneration rate

11Patient Discharge Instructions/pdi26

copy discharge instructions

›What happened and why you are going home

›You have been diagnosed with an injury to the median nerve in your wrist or forearm

›This nerve controls feeling and movement in your thumb, index finger, middle finger, and part of your ring finger

›Your injury appears stable and does not require surgery at this time

›You have been given a splint to protect the area and prevent further injury

›How to care for yourself at home

›Keep your wrist splint on as instructed — do not remove it unless told to do so

›Keep your hand elevated above the level of your heart as much as possible to reduce swelling

›Take pain medications as prescribed — take with food to protect your stomach

›Keep any wounds clean and dry as instructed

›Do not put any tight bandages or jewelry on your hand or wrist

›Activity restrictions

›Avoid activities requiring grip strength or fine pinch until cleared by your follow-up provider

›Do not drive or operate machinery if your hand is weak or numb

›Keep your follow-up appointment — this is critical for monitoring your nerve recovery

›Return to the emergency department immediately if

›Numbness or tingling in your thumb, index, or middle finger is getting worse

›Pain is increasing — especially if it is getting worse under a cast or splint

›New weakness develops in your hand (difficulty gripping or pinching)

›Your fingers become cold, pale, blue, or significantly swollen

›Fever, wound redness, drainage, or signs of infection develop

›You feel your cast or splint is too tight

›Follow-up plan

›Return to see your hand specialist or surgeon in 48 to 72 hours for reassessment

›Wound check at 1 to 2 weeks

›Nerve conduction studies will be arranged at 3 to 4 weeks to assess your nerve function

12References/r20

Guidelines and key sources

›Kim DH, Kam AC, Chandika P, Tiel RL, Kline DG. Surgical Management and Outcomes in Patients With Median Nerve Lesions. Journal of Neurosurgery. 2001. PMID 11596952

›30-year surgical series establishing outcome benchmarks for neurolysis, suture repair, and graft repair

›Thomson SE, Ng NY, Riehle MO, et al. Bioengineered Nerve Conduits and Wraps for Peripheral Nerve Repair of the Upper Limb. Cochrane Database of Systematic Reviews. 2022

›Evidence base for nerve conduit use in gaps requiring bridging

›Holbrook HS, Hillesheim RA, Weller WJ. Acute Carpal Tunnel Syndrome and Median Nerve Neurapraxia: A Review. Orthopedic Clinics of North America. 2022. PMID 35365264

›Key distinction between ACTS (surgical emergency) and neurapraxia (conservative management)

›Pederson WC. Median Nerve Injury and Repair. Journal of Hand Surgery. 2014. PMID 24862118

›Comprehensive review of classification, management, and outcomes

›Shields LBE, Iyer VG, Zhang YP, Shields CB. Proximal Median Nerve Neuropathy: Electrodiagnostic and Ultrasound Findings in 62 Patients. Frontiers in Neurology. 2024. PMID 39703354

›Iatrogenic etiology in 48.4% of proximal median nerve injuries; ultrasound utility

Neuropathic pain and electrodiagnostic references

›Finnerup NB, Attal N, Haroutounian S, et al. Pharmacotherapy for Neuropathic Pain in Adults: A Systematic Review and Meta-Analysis. Lancet Neurology. 2015. PMID 25575710

›Evidence base for gabapentinoids, duloxetine, and tricyclics in neuropathic pain

›Pripotnev S, Bucelli RC, Patterson JMM, et al. Interpreting Electrodiagnostic Studies for the Management of Nerve Injury. Journal of Hand Surgery. 2022. PMID 35738957

›Timing and interpretation of NCS and EMG for nerve injury assessment

›Bateman EA, Pripotnev S, Larocerie-Salgado J, Ross DC, Miller TA. Assessment, Management, and Rehabilitation of Traumatic Peripheral Nerve Injuries for Non-Surgeons. Muscle and Nerve. 2025

›Comprehensive non-surgical management and rehabilitation framework

›Wassef C, Chrabolowski J, Cheng F, et al. The Risk of Acute Carpal Tunnel Syndrome in Lunate and Perilunate Dislocations. Journal of Hand Surgery. 2026. PMID 41934453

›25% incidence of acute median neuropathy with lunate and perilunate dislocations

›Silver S, Ledford CC, Vogel KJ, Arnold JJ. Peripheral Nerve Entrapment and Injury in the Upper Extremity. American Family Physician. 2021. PMID 33630556

›Diagnostic test sensitivity and specificity for median nerve clinical tests

Evidence & Review

Evidence & Review