Assessment of peripheral nerve surgery

Mr Vaikunthan Rajaratnam MBBS(Mal),AM(Mal),FRCS(Ed),FRCS(Glasg),FICS(USA),MBA(USA),

Dip Hand Surgery(Eur),PG CertMedEd(Dundee),FHEA(UK),AFFST(Ed),FAcadMEd(UK).

Senior Consultant Hand SurgeonAlexandra Health, SINGAPORE

At the end of the lecture the participant will be able to:

• 1. List the qualitative and quantitative methods for nerve function understanding their limitations

• 2. Understand the role of electro diagnosis in nerve injury

Issues & Challenges

• cortical functional reorganization of hand representation result of axonal misdirection - cortical remapping

• Modulation of central nervous processes rather than peripheral factors

• Brain capacity for visuo-tactile and audio-tactile interaction• selective de-afferentation enhancing the effects of sensory

relearning• no surgical technique which can ensure recovery of tactile

discrimination in the hand of an adult after median nerve lesion

• hand as a sense organ• MRC Scale subjective findings - psychometric drawbacks

Regeneration after nerve repair

regardless of the repair technique - axonal misdirection is unavoidable

Assessment of hand function

• sensibility • motor function• autonomic • pain and • discomfort

Model Instrument for OutcomeAfter Nerve Repair

• Detection tests - Semmes-Weinstein monofilaments,

• discrimination tests - two-point discrimination (2PD),

• identification tests- shape/texture-identification (STI) test

• activities of daily living (ADL) - The DASH was also the most commonly used condition-specific patient-reported outcome in the included clinical trials

• (McPhail, Bagraith, Schippers, Wells, & Hatton, 2012)

Factors influencing the outcome• Age• Cognitive brain capacities - Verbal learning capacity and

visuo-spatial cognitive capacity

• Timing of repair• Type of nerve• Level of injury• Type of injury• role of the brain in functional recovery - ‘new

language spoken by the hand’.

What happens in the brain after nerve injury and repair

• silent ‘black hole• adjacent cortical areas expand and occupy the

former• distorted discontinuous islands

Sensory re-education and sensoryrelearning

• mind does not understand the new ‘sensory code’ associated with specific textures and shapes

• touch modalities, localise touch, shapes and textures

• concepts of learning mechanisms, cortical remodelling and brain plasticity

New strategies in sensory re-education and sensory relearning

• Phase 1: maintaining the cortical hand map activate the cortical area representing the damaged nerve- visuo-tactile and audio-tactile interaction

• Activation of motor neurones – ‘mirror neurones’ in premotor cortex by the mere observation of hand motor actions

• activated by reading/listening to action or words• Phase 2: enhancing the effects of sensory re-

educationde-afferentation of the forearm would hypothetically result in expansion of the adjacent cortical hand representation• Cutaneous de-afferentation of the forearm

(Rizzolatti et al. 2001, Rizzolatti & Craighero 2004)

Outcomes

• outcome shows ongoing improvements up to 5 years after the nerve repair

• 59% of patients with median or ulnar nerve repairs returned to work within 1 year with an average time off work of 31 weeks (Jaquet 2004)

• high education, high compliance to hand therapy and an isolated injury predict quicker return to work in patients with median and/or ulnar nerve injuries.

Sollerman Hand Function Test

• overall measure of hand and grip function when engaging in ADLs (Sollermen & Ejeskar 1985).

• It was designed to measure grips that are needed for certain ADLs such as eating, driving, personal hygiene, and writing.

• includes subtests that represent common handgrips (volar, transverse volar, spherical volar and pinch positions - pulp, lateral, tripod, and the five finger) and activities (using a key; picking up coins from a flat surface; writing with a pen; using a phone; and pouring water from a jug)

Nerve Conduction Studies and Electromyography in theEvaluation of Peripheral Nerve Injuries

NCS & EMG

• essential in the evaluation of nerve disorders• localizing the site of injury• distinction of conduction block from axonal

degeneration• prognostic information• dependent on the skills of the examiner• Augment physical examination

NCS and Needle EMG

• measurement of nerve response amplitude and conduction velocity along the course of each nerve

• sensory nerve action potential (SNAP) 5–20 mV in amplitude orthodromically/antidromically

• compound motor action potential (CMAP)• Needle EMG distinguish neurogenic /

myopathic causes

Post Injury - acute

• Motor axons remain excitable for up to 7 days after injury. Sensory axons to 11 days

• So perform 14 days post injury• Spontaneous activity in muscles - 2 – 6 weeks

References• Lundborg G, Rosén B. Hand function after nerve repair. Acta Physiologica February

2007;189(2):207-217 • McPhail, S. M., Bagraith, K. S., Schippers, M., Wells, P. J., & Hatton, A. (2012). Use

of Condition-Specific Patient-Reported Outcome Measures in Clinical Trials among Patients with Wrist Osteoarthritis: A Systematic Review. Advances in orthopedics, 2012,

• Jaquet, J. 2004. Median and minor nerve injuries: Prognosis and predictors for clinical outcome. Thesis. Department of Plastic and Reconstructive Surgery, Erasmus Medical Center, Erasmus University, Rotterdam