management of the patient with a neurological deficit · asura 2012. be prepared to educate to...
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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