Plexopathies – Electrodiagnostic approach Charles Kassardjian MD MSc FRCPC St. Michael’s Hospital University of Toronto 1 Disclosures • Advisory board for Akcea, Sanofi Genzyme, Takeda, Alexion, and speaker fees from Sanofi Genzyme and Alexion 2 Learning Objectives 1. To outline the electrodiagnostic approach to the patient presenting with a possible plexopathy (brachial or lumbosacral) 2. To describe the clinical and electrophysiological findings of brachial and lumbosacral plexopathies 3. Highly recommend: Focal Peripheral Neuropathies by John D. Stewart 3 1 Definitions • We will only discuss the brachial and lumbosacral plexi today • Peripheral nervous system structures – Complex anatomy – Input from multiple nerve roots – Contribute to major peripheral nerves supplying limbs – “Post-ganglionic” – Not as commonly injured as nerve roots or peripheral nerves 4 Case 1 • 56M, healthy apart from nasopharyngeal carcinoma diagnosed 5 years earlier and treated with chemotherapy and radiation therapy • 1-2 years after therapy noted restricted neck movements and tightening of the muscles around his neck • 3-4 years after therapy noted sensory symptoms in the medial right hand and forearm, followed by weakness of the right hand and shoulder 1/26/21 5 Case 1 • Examination: – CN normal (no Horner’s) – Weakness of R deltoid, biceps, triceps, finger extensors and finger abductors (all around 4/5) – R 1+ biceps, triceps and brachioradialis reflexes – Pinprick impairment over the medial right hand (4th and 5th digits, medial palm) and forearm 1/26/21 6 2 Clinical features • History is critical – Temporal course: Acute (post-injury), Subacute (days to weeks), Chronic +/- Progressive – Preceding event or risk factors: Trauma, infection, diabetes, cancer – Presence of pain and relation to other symptoms – Pattern of weakness – Distribution of sensory symptoms 1/26/21 7 Differential diagnosis • Cervical or lumbosacral radiculopathy • Cervical myelopathy • Mononeuropathy or multiple mononeuropathies • Motor neuron diseases • MSK (shoulder, hip) 1/26/21 8 Why do EDX? • Localize the lesion (plexus, root, nerve) • Identify pattern of involvement (component of plexus, typical “nerves” like AIN or suprascapular) • Severity and timing of lesion • Axonal vs. Demyelinating • Reinnervation and “continuity”: Especially in traumatic plexopathies 1/26/21 9 3 Plexopathies – EDX Principles • Plexopathies are POST-ganglionic lesions – If axonal loss à Low amplitudes on motor and sensory NCS – Vs. Radiculopathies where the lesion is preganglionic to dorsal root ganglion à Normal sensory NCS • If pure plexopathy: Needle examination of paraspinal muscles should be normal 1/26/21 10 Other investigations • MRI: – Useful to evaluate for: Infiltrative lesions, compression, inflammatory changes or enlargement • Ultrasound (more for brachial): – Able to image multiple components of the plexus – Can be done at the time of EDX • X-ray of C-spine: – Screen for cervical rib or elongated C7 transverse process • Blood work: – Screening for inflammatory, metabolic, systemic disease 1/26/21 11 Anatomy – Brachial plexus Aids to the Examination of the PNS, 2000 12 4 Anatomy – Brachial plexus • “Supraclavicular plexus” • Nerve roots + Trunks • Upper, Middle and Lower trunks • More common than “infraclavicular” • Etiological differences Aids to the Examination of the PNS, 2000 13 Anatomy – Brachial plexus • “Retroclavicular plexus” • Divisions • Anterior and posterior divisions Aids to the Examination of the PNS, 2000 14 Anatomy – Brachial plexus • “Infraclavicular plexus” • Cords and proximal components of peripheral nerves • Lateral, Posterior, and Medial cords Aids to the Examination of the PNS, 2000 15 5 Brachial plexopathies - NCS Study Component evaluated Median motor - APB Lower trunk, Medial cord Ulnar motor – ADM, FDI Lower trunk, Medial cord Radial motor – EDC, EIP Middle trunk/Lower trunk, Posterior cord Median sensory – D2 Upper trunk, Lateral cord Ulnar sensory – D5 Lower trunk, Medial cord Radial sensory Upper trunk, Posterior cord Lateral antebrachial cutaneous Upper trunk, Lateral cord Medial antebrachial cutaneous Lower trunk, Medial cord 1/26/21 16 Brachial plexopathies - NCS Rubin, 2020 1/26/21 17 Brachial plexopathies – NCS • Most are axonal lesions: – Expect low amplitude responses (CMAP, SNAP) in distribution of lesion – Relative sparing of conduction velocity, latencies 1/26/21 18 6 Brachial plexopathies – Needle Exam • Sparing of paraspinals in pure plexopathy • Etiologic clue: Myokymic discharges in radiation plexopathy • Reduced recruitment • Fibrillation potentials/PSWs • Large motor unit potentials • Early re-innervation and “nascent” MUPs 1/26/21 19 Brachial plexopathies – Etiologies Inflammatory Parsonage-Turner syndrome Diabetic cervical radiculoplexus neuropathy Multifocal forms of CIDP Infectious VZV radiculoplexopathy Traumatic Penetrating Non-penetrating Birth (e.g. Erbs or Dejerine-Klumpke palsies) Burners and Stingers Neoplastic Primary neural tumours Metastatic invasion Radiation Genetic Hereditary neuralgic amyotrophy (SEPT9) HNPP Compressive True neurogenic thoracic outlet syndrome Post-sternotomy 1/26/21 20 Case 1 • 56M, healthy apart from nasopharyngeal carcinoma diagnosed 5 years earlier and treated with chemotherapy and radiation therapy • 1-2 years after therapy noted restricted neck movements and tightening of the muscles around his neck • 3-4 years after therapy noted sensory symptoms in the medial right hand and forearm, followed by weakness of the right hand and shoulder 1/26/21 21 7 Case 1 • Examination: – CN normal (no Horner’s) – Weakness of R deltoid, biceps, triceps, finger extensors and finger abductors (all around 4/5) – 1+ biceps, triceps and brachioradialis reflexes – Pinprick impairment over the medial right hand and forearm 1/26/21 22 NCS Motor Nerve Amplitude CV (m/s) DL (ms) R Median 4.2 53 3.9 R Ulnar 3.5 51 2.7 Sensory Nerve R Median 5 3.5 L Median 18 3.1 R Ulnar 5 3.1 L Ulnar 17 2.5 R Radial 6 2.3 L Radial 24 2.3 R MABC 3 2.7 L MABC 8 2.6 R LABC 3 2.8 L LABC 5 2.5 1/26/21 23 Needle exam • Fasciculation potentials and large MUPs in the biceps, deltoid, FDI and FPL 1/26/21 24 8 Other investigations and diagnosis • MRI of the cervical spine and right brachial plexus: Unremarkable • Diagnosis: Radiation-induced right brachial plexopathy 1/26/21 25 Radiation plexopathy • Radiation often for breast, head, neck or lung ca • RF: Dose of radiation • Any part of the plexus can be involved • Present with paresthesias, numbness, weakness and atrophy, slowing progressing • Variable delay from radiation: Months to many years 1/26/21 26 Evaluation • EMG: – Myokymic discharges more common in radiation plexopathy vs. neoplastic (about 60% of patients) (Harper et al. 1989) • Imaging: – Often performed to rule out neoplastic invasion – May see T2 hyperintensity, but often normal • Treatment: – Supportive – Either slow decline or stabilization in most patients 1/26/21 27 9 Case 2 • 74M presents with 6 weeks of burning and stabbing pain in the right arm, radiating from the shoulder – Weakness of the right arm subsequently developed about a week later, including wrist and finger drop • 2 weeks prior to neurological symptoms, developed a vesicular rash on the dorsum of the right arm and forearm 1/26/21 28 Case 2 Motor Nerve Amplitude CV (m/s) DL (ms) R Median 6.9 51 3.9 R Ulnar 3.8 51 3.1 Sensory Nerve R Median 9 3.5 L Median 12 3.3 R Ulnar NR -- L Ulnar 9 3.0 R Radial NR -- 1/26/21 29 Case 2 1/26/21 30 10 Case 2 • Swab of vesicle positive for VZV (was already treated with acyclovir for presumed shingles zoster) • Over next 2 months, patient’s symptoms improved (pain, sensory), and strength gradually improved (not to baseline) 1/26/21 31 Case 2 1/26/21 32 Zoster associated limb paresis • Large series (49 patients) with vesicular eruption + weakness of same limb within 30 days of rash (Jones et al. 2014) • Mean age 71, 67% were men • Most had prolonged weakness (~200 d) and few had complete resolution 1/26/21 33 11 Zoster associated limb paresis Jones et al, 2014 1/26/21 34 Zoster associated limb paresis Jones et al, 2014 1/26/21 35 Zoster associated limb paresis • MRI: About 25-60% of the time may show nerve enlargement or T2 hyperintensity (no enhancement) Zubair et al. 2017 1/26/21 36 12 Neuralgic amyotrophy • Immune-mediated process • Not really a “plexopathy” as much as multiple neuropathies • Associations: Viral infections, vaccines, trauma, pregnancy, surgery, exercise 1/26/21 37 Neuralgic amyotrophy • Acute-subacute onset of arm and shoulder pain • Weakness: Usually days to weeks later, as pain subsiding • Any part of the plexus, but often weakness in distribution of specific nerves – Arising from plexus: Suprascapular nerve, axillary, AIN – Or not arising from plexus: LTN, phrenic • Can be bilateral in 20-30% 1/26/21 38 Neuralgic amyotrophy Ferrante and Wilbourn, 2017 1/26/21 39 13 Imaging in Neuralgic amyotrophy • MRI may show T2 hyperintensities – Either in specific portions of the plexus – Or in individual nerves distal to plexus – Or in specific fascicles destined to be nerve branches (e.g. AIN, Pham et al. 2014) 1/26/21 40 Imaging in Neuralgic amyotrophy • Hour-glass constrictions of nerve – May correlate with persisting deficits – Indication for surgical exploration and neurolysis? Sneag et al 2017 1/26/21 41 Neuralgic amyotrophy • Varied descriptions of prognosis: Most generally favorable (improvement between 1-3 years), while recent studies suggest many have persisting deficit at 3 years • No evidence-based treatment