MONONEUROPATHY is a topic covered in the Harrison's Manual of Medicine.

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Clinical Features

Mononeuropathies are usually caused by trauma, compression, or entrapment. Sensory and motor symptoms are in the distribution of a single nerve—most commonly the ulnar or median nerve in the arm or peroneal (fibular) nerve in the leg. Intrinsic factors making pts more susceptible to entrapment include arthritis, fluid retention (pregnancy), amyloid, hypothyroidism, tumors, and diabetes mellitus. Clinical features favoring conservative management of median neuropathy at the wrist (carpal tunnel syndrome) or ulnar neuropathy at the elbow include sudden onset, no motor deficit, few or no sensory findings (pain or paresthesias may be present), and no evidence of axonal loss by EMG. Surgical decompression is considered for chronic mononeuropathies that are unresponsive to conservative treatment if the site of entrapment is clearly defined. The most common mononeuropathies are summarized in Table 193-3.

TABLE 193-3: MONONEUROPATHIES
 SymptomsPrecipitating ActivitiesExaminationElectro-DiagnosisDifferential DiagnosisTreatment
Carpal tunnel syndromeNumbness, pain or paresthesias in fingersSleep or repetitive hand activity

Sensory loss in thumb, second, and third fingers

Weakness in thenar muscles; inability to make a circle with thumb and index finger Tinel sign, Phalen maneuver

Slowing of sensory and motor conduction across carpal tunnelC6 radiculopathy

Splint

Surgery definitive treatment

Ulnar nerve entrapment (UNE) at the elbowNumbness or paresthesias in ulnar aspect of handElbow flexion during sleep; elbow resting on desk

Sensory loss in the little finger and ulnar half of ring finger

Weakness of the interossei and thumb adductor; claw-hand

Focal slowing of nerve conduction velocity at the elbow

Thoracic outlet syndrome

C8–T1 radiculopathy

Elbow pads

Avoid further injury

Surgery when conservative treatment fails

UNE at the wristNumbness or weakness in the ulnar distribution in the handUnusual hand activities with tools, bicyclingLike UNE but sensory examination spares dorsum of the hand, and selected hand muscles affectedProlongation of distal motor latency in the handUNEAvoid precipitating activities
Radial neuropathy at the spiral grooveWrist dropSleeping on arm after inebriation with alcohol—”Saturday night palsy”Wrist drop with sparing of elbow extension (triceps sparing); finger and thumb extensors paralyzed; sensory loss in radial region of wrist

Early—conduction block along the spiral groove

Late—denervation in radial muscles; reduced radial SNAP

Posterior cord lesion; deltoid also weak

Posterior interosseous nerve (PIN); isolated finger drop

C7 radiculopathy

Splint

Spontaneous recovery provided no ongoing injury

Thoracic outlet syndromeNumbness, paresthesias in medial arm, forearm, hand, and fingersLifting heavy objects with the handSensory loss resembles ulnar nerve and motor loss resembles median nerveAbsent ulnar sensory response and reduced median motor responseUNESurgery if correctable lesion present
Femoral neuropathyBuckling of knee, numbness or tingling in thigh/medial legAbdominal hysterectomy; lithotomy position; hematoma, diabetesWasting and weakness of quadriceps; absent knee jerk; sensory loss in medial thigh and lower legEMG of quadriceps, iliopsoas, paraspinal muscles, adductor muscles

L2–4 radiculopathy

Lumbar plexopathy

Physiotherapy to strengthen quadriceps and mobilize hip joint

Surgery if needed

Obturator neuropathyWeakness of the leg, thigh numbnessStretch during hip surgery; pelvic fracture; childbirthWeakness of hip adductors; sensory loss in upper medial thighEMG—denervation limited to hip adductors sparing the quadriceps

L3–4 radiculopathy

Lumbar plexopathy

Conservative management

Surgery if needed

Meralgia parestheticaPain or numbness in the anterior lateral thigh

Standing or walking

Recent weight gain

Sensory loss in the pocket of the pant distributionSometimes slowing of sensory response can be demonstrated across the inguinal ligamentL2 radiculopathyUsually resolves spontaneously
Peroneal nerve entrapment at the fibular headFootdropUsually an acute compressive episode identifiable; weight loss

Weak dorsiflexion, eversion of the foot

Sensory loss in the anterolateral leg and dorsum of the foot

Focal slowing of nerve conduction across fibular head

Denervation in tibialis anterior and peroneus longus muscles

L5 radiculopathyFoot brace; remove external source of compression
Sciatic neuropathyFlail foot and numbness in footInjection injury; fracture/dislocation of hip; prolonged pressure on hip (comatose pt)Weakness of hamstring, plantar and dorsiflexion of foot; sensory loss in tibial and peroneal nerve distribution

NCS—abnormal sural, peroneal, and tibial amplitudes

EMG—denervation in sciatic nerve distribution sparing glutei and paraspinal

L5–S1 radiculopathies

Common peroneal neuropathy (partial sciatic nerve injury)

LS plexopathies

Conservative follow up for partial sciatic nerve injuries

Brace and physiotherapy

Surgical exploration if needed

Tarsal tunnel syndromePain and paresthesias in the sole of the foot but not in the heelAt the end of the day after standing or walking; nocturnal

Sensory loss in the sole of the foot

Tinel sign at tarsal tunnel

Reduced amplitude in sensory or motor components of medial and planter nervesPolyneuropathy, foot deformity, poor circulationSurgery if no external cause identified

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Citation

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TY - ELEC T1 - MONONEUROPATHY ID - 623486 Y1 - 2017 PB - Harrison's Manual of Medicine UR - https://harrisons.unboundmedicine.com/harrisons/view/Harrisons-Manual-of-Medicine/623486/all/MONONEUROPATHY ER -