MONONEUROPATHY

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 196-3.
TABLE 196-3: 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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