Management of the patient with a neurological deficitMichael BarringtonASURA 2012

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Perioperative nerve injury within 3 months TKA:Not associated with peripheral nerve blockade or

anaesthesia typeIncreased risk with increased age and tourniquet

time

Orthopaedic procedures❖ Higher risk for perioperative nerve injuries

❖ Physical factors - force/positioning

❖ Tourniquet neuropathy

❖ e.g. Total knee arthroplasty: 2.2 % incidence of peroneal nerve palsy, increases to 7.7 % with prolonged tourniquet inflation

❖ L5-s1 radiculopathy may render sciatic nerve more sensitive to ischaemia and traction

Brachial plexus

❖ Long mobile and complex structure abutting rigid bony and ligamentous structures

❖ Tethered medially to the vertebral transverse processes and laterally to the axillary fascia

❖ At risk of stretch or compression injuries

Ulnar neuropathy at elbow❖ With elbow extension

❖ ulnar groove is smooth, round and capacious

❖ In flexion

❖ nerve is flattened, tortuous in a narrow canal with aponeurosis pulled tightly across it

❖ In supination: olecranon wears the pressure,

❖ In pronation the nerve in the groove is more exposed

Ulnar neuropathy at elbow

❖ Elbow flexion and pronation of forearm places ulnar nerve at at greatest risk

❖ Nerve may sublux and wear full brunt of the compression

❖ Nerve conduction studies can distinguish between a proximal brachial plexopathy and ulnar neuropathy

Neurologic sequelae transitoryDistal mononeuropathies

Initial management

❖ Consider causes of perioperative nerve injury other than regional anaesthesia

❖ Thorough clinical assessement: history, examination

❖ Are the features consistent with nerve/plexus block performed?

❖ History of anticoagulation relevant for neuraxial and deep peripheral blocks

Referral to other specialists

❖Radiologist

❖Neurologists

❖Electrophysiologists

❖Chronic pain

Triggers for referral❖ New onset of motor or sensory deficit

❖ Non-resolving

❖ paraesthesia (wait one month)

❖ pain

❖ allodynia or dysaesthesia

❖ (Concern exhibited by surgical team)

Electrophysiology

❖ Nerve conduction studies (NCS)

❖ Electromyography (EMG)

❖ NCS and EMG are extension of physical examination

❖ Important role in disabling peripheral neuropathies

Electrophysiology❖ May locate the site of the deficit but not always

diagnose cause

❖ Labour intensive, operator dependant, intrinsic limitations

❖ Comparison with non-surgical limb may be important

❖ Don’t always give a definitive answer in the postoperative period

Timing of NCS/EMG

❖ Pathological changes may take 3 - 5 weeks postoperatively to develop

❖ Alternately, NCS/EMG abnormalities in the early postoperative period may indicate preexisting neuropathy

❖ Sequential studies may be required

Measurements

❖ Conduction velocities

❖ Compound Muscle Action Potential (CMAP) (size and shape)

❖ F-waves

❖ EMG examine muscles along the known course of a nerve

MRI

❖ Compressive lesion

❖ Limited utility in diagnosing intrinsic disease of nerves

❖ Signal characteristics of muscles innervated by nerve being examined

Conclusion❖ Be prepared

❖ Perioperative neuropathies diverse aetiology

❖ Higher risk scenarios

❖ Most neurological features are transitory

❖ NCS/EMG don’t always provide all the answers

❖ Often the diagnosis in one of exclusion