Management of Neuropathic Pain Following Peripheral Nerve Injury – The Pain Medicine Consultant's Perspective Dr. Andreas Goebel PhD FRCA FFPMRCA Director Pain Research Institute Senior Lecturer and Honorary Consultant in Pain Medicine University of Liverpool and Walton Centre NHS Foundation Trust, UK Cambridge Annual Medico-Legal Conference

‘Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’ International Association for the Study of Pain ‘‘Neuropathic pain’ is pain arising as a direct consequence of a lesion or disease affecting the somatosensory system.’ Treede et al., 2012

Causes for peripheral post-traumatic neuropathies -Trauma: i) compressive neuropathy: crush injury (acute, single trauma), or chronic nerve compression (Seddon/Sunderland criteria); ii) non-compressive injuries -Perioperative injury: surgical or local anaesthesia. Examples: post- mastectomy pain, post-thoracotomy pain, post-herniotomy pain, pain post amputation Note: SEVERITY OF INJURY ≠ PAIN INTENSITY TYPE OF INJURY ≠ PAIN INTENSITY

Grading of certainty for the presence of neuropathic pain: definite – all (1 to 4), probable 1 and 2 plus either 3 or 4, possible 1 and 2 without confirmatory evidence from 3 or 4 *region corresponding to a peripheral innervation territory + with temporal relationship to pain typical for the condition ++ these tests confirm the presence of negative or positive neurological signs concordant with the distribution of pain. May be supplemented by objective tests. § confirmatory tests depend on which lesion or disease is causing the pain

Borsook et al., 2013

Brachial plexus avulsion (rare); 90% patients can have pain, number of roots disrupted is relevant

The Pain Medicine Consultant’s Assessment History including any pain before surgery/pain history; other pains; pain intensity; mediciation, pain impact; social situation; past medical history Examination, including positive and negative sensory signs, touch, pressure, cold, warm – extend of painful area Questionnaires – Hospital Anxiety and Depression Scale, Brief Pain Inventory, Pain Catastrophizing Scale ?? In a medico-legal setting: resilience, perceived injustice

HADS (A=Anxiety, D=Depression)

Brief Pain Inventory

Pain catastrophizing scale (PCS) – indicating the level of unhelpful beliefs about pain, and the grade of an unhelpful coping style

Management (non-avulsion neuropathic pains): i)Information (‘why do I have this pain’, prognosis) – note: prognosis is generally considered to become rather stable after 2 years i)Psychological support – most patients will develop distress. Information about ‘pain management’ approaches, e.g. information leaflet about a cognitive behavioral pain management program (PMP) ii)Physiotherapy – may improve functioning in spite of pain, is part of PMP iii)Drugs – Neuropathic pain drugs in accordance with EFIC guidelines (tricyclics, gabapentinoids, SNRIs, second line opioids); combinations. Note: most drugs will loose efficacy over time iv)Topical therapy: high concentration capsaicin patch (8%) – every 3 months; lignocaine patch for sensitivity. v)Neuromodulation: external peripheral nerve stimulation, implanted peripheral nerve stimulation, spinal cord stimulation, dorsal root ganglion stimulation

Pain Management Program

8% Capsaicin patch: one of few innovations in Pain Medicine over the past 10 years – has made a tangible difference to this group of patients

External peripheral nerve stimulator treatment, for home- application

Dorsal Root Ganglion Stimulation

Brachial Plexus Avulsion (e.g. motor bike accidents) Mixed central and peripheral neuropathic pain Often accompanied by phantom limb pain Collaboration with Neurosurgical colleagues, consideration of DREZ lesioning Brain training methods may reduce phantom limb pain Specialist Centre!

‘Recent research suggests that perceived injustice consequent to injury might represent one of the strongest predictors of problematic outcomes’ Michael Sullivan (McGill)

Conclusions Neuropathic pain after peripheral nerve injury can be either iatrogenic after surgery/ regional anesthesia, or may originate from other trauma Such pains are diagnosed according to recent, standardized criteria (Treede et al.). The natural course of neuropathic pains after nerve injury is considered generally stable from 2 years onwards The nature of the insult, and the type of injury do not generally predict the patient’s pain quality/intensity; not every patient will develop chronic pain, even after severe nerve injury Pain management is ‘multimodal’ and should generally include information. It may also include psychological support, physiotherapy, drugs, patches, and neuro-modulation. Brachial plexus avulsions are mixed neuropathic pains. These patients should be treated at tertiary centres, and may need neurosurgical input Appreciation of a patient’s psychosocial state should help their solicitor to optimize understanding of the case – questionnaires can help