Limb Nerve Roots and Sensation Pathways: A Tutor's Guide for Finals

1. Limbs: Tutor Information PULSE: Preparation for Finals Tutor name

2. Resource summary • Common viva questions/topics • Case-based additional information (Cases 1 – 9)

3. Common questions • Things you might pick up and questions you will get asked…

4. UMN vs LMN

5. What are the motor nerve roots for the upper limb? • There is a difference between assessing nerve roots and nerves; but in general they can both be done in the same series of movements • C5 = shoulder abduction (axillary) • C6 = elbow flexion (musculocutaneous) • C7 = wrist extension (radial) • C8 = finger flexion (median/ulnar) • T1 = finger abduction (ulnar) • T1 = thumb abduction (median)

6. What are the motor nerve roots for the lower limb? • L1/2 = hip flexion • L3/4 = knee extension • L4 = ankle dorsiflexion • L5 = big toe extension • S1 = ankle plantarflexion • L5/S1 = knee flexion • L5/S1 = hip extension

7. What are the nerve roots for the limb reflexes? • S1/2 = ankle • L3/4 = knee • C5/6 = biceps, supinator • C7/8 = triceps • Reinforcement if can’t find reflex

8. What are the main pathways of sensation? Again remember to use sternum as reference point, and get patient to close their eyes • Different modalities; • Light touch and proprioception = dorsal column • Pain and temperature = spinothalamic tract

9. What are the nerve roots for sensation in the upper limb? • C4 = shoulder tip • C5 = regimental badge • C6 = tip of thumb (6 shooter) • C7 = tip of middle finger (7-up) • C8 = tip of little finger • T1 = medial mid-forearm

10. What are the nerve roots for sensation in the lower limb? • L2 = upper thigh • L3 = above knee (3 the knee) • L4 = medial mid-leg • L5 = dorsum of foot • S1 = lateral sole of foot (stand on S1)

11. What are the causes of peripheral neuropathy? • ABCDE-O • Alcohol (mixed) • B12 deficiency (mixed) • Chronic renal failure (sensory) • Diabetes (sensory) • Every vasculitis (mixed) • Others - Guillain-Barre (motor), lead poisoning (motor), paraneoplastic (mixed), amyloid (mixed), Lyme disease

12. What are the causes of proximal myopathy? • Muscular dystrophy • Poly and dermatomyositis • Cushings, Acromegaly, thyrotoxicosis • Diabetic amyotrophy • Etoh, statins, steroids • Paraneoplastic

13. What is Froment’s sign? • Froments = ulnar nerve palsy; loss of thumb adduction • FrOments - makes an O shape

14. What are the causes of a positive prayer sign? • Fixed flexion deformity of the fingers • RA • Scleroderma • Diabetes • Ulnar nerve palsy (partial claw hand) • T1 palsy (complete claw hand) • Dupytren’s contracture

15. What are the manifestations of a T1 nerve root lesion? • Seen in e.g. Pancoast tumours • Horners syndrome - ptosis, miosis, anhydrosis • Pain/sensory loss in axilla • Complete claw hand • Wasting of interossei

16. Case 1

17. To complete my examination… • Full cranial nerve examination (homonymous hemianopia, visual defects) • Assessment of higher cognitive function – speech (dominant hemisphere) and sensory inattention (non-dominant hemisphere) • Cardiovascular examination – including BP, Carotid bruits and murmurs, AF, • Cardiovascular history - modifiable risk factors

18. Differential Diagnoses • Vascular – ischaemia, infarction, embolism, heamorrhage • SOL – malignancy, abcess, hydrocephalus • Inflammatory – MS, Consider the age of the patient when ranking these.

19. Where is the lesion? Classify by site and/or by artery involved….

22. Causes of Stroke Ischaemic (85%) • Atherosclerosis • Dissection • Vasculitis • Injury (inc iatrogenic) • Spasm (migraine) • Embolus (cardiac – AF, IE) • Occlusion • Hypercoaguable states (e.g. hereditary, OCP, polycythaemia, neoplasia) Haemorrhagic (15%) • HTN • Aneurysms • Elderly • Malformations • Autoimmune (vasculitis) • Toxin (warfarin) • Other – haemorrhagic transformation • Mets/primary brain tumour • Accident – head injury

23. Case 2

24. What are the causes of a peripheral neuropathy? Physical trauma • Compression • Pinching • Cutting • Projectile injuries • Strokes including prolonged occlusion of blood flow Others • Shingles • Malignant disease • HIV • Radiation • Chemotherapy Genetic • Charcot-Marie-Tooth syndrome • Friedrich’s ataxia Metabolic/endocrine • DM • Chronic renal failure • Porphyria • Amyloidosis • Liver failure • Hypothyroidism Inflammatory disease • Guillain-Barré syndrome • SLE • Leprosy • Sjogren’s Toxic Alcohol Drugs • Fluoroquinolones • Vincristin • Phenytoin • Nitrofurantoin • Isoniazid Organic metals Heavy metals Excess Vit B6 (pyridoxine) Vit deficiency • B12 • A • E • B1 Most common causes: DM Alcohol Vitamin deficiency

25. Case 3

26. Brown-Sequard Syndrome Causes • Degenerative disease of the spine • Syringomyelia • Cord tumour • Haematomyelia • MS • Angioma • Trauma, e.g. bullet or stab wounds • Myelitis • Post-radiation myelopathy • Motor changes • Ipsilateral UMN signs below the hemisection (corticospinal tract) • LMN signs at the level of hemisection on the same side • Sensory changes • Contralateral pain and temperature loss (upper level of sensory loss usually a few segments below the level of the lesion) spinothalamic tract • Ipsilateral vibration and proprioception loss (dorsal column) • In segment of lesion – ipsilateral anaesthesia and zone of hyperaesthesia

30. Case 4

31. O/E Lower limbs • Increased tone and brisk reflexes • Upgoingplantars bilaterally Upper limbs • Decreased pin-prick in hands • Atrophy and weakness of hand muscles Diagnosis… Cervical Myelopathy

32. Case 5

33. Localise the Lesion • Peripheral Neuropathy • ‘Glove and Stocking’ • Likely cause: EtOH XS (+/- B1 deficiency) • Particular causative diseases have predilection for specific nerves or fibre types and for certain components of the nerve course… • Mononeuropathy (tend to be unilateral) – CTS, CPNP • Mononeuritis multiplex – vasculitis, diabetes • Polyneuropathy (diffuse, symmetrical fashion)… • Autonomic neuropathy – diabetes, amyloidosis, GBS

34. Peripheral Neuropathy Aetiology • Inflammatory – GuillainBarré Syndrome, CIDP, RA, SLE, vasculitis • Infective - Leprosy • Toxic – EtOH (+ thiamine deficiency), Drugs (chemo) • Metabolic – Diabetes, Hypothyroid, CKD • Idiopathic (one third of cases cause unknown) • Neoplastic – paraneoplastic, MGUS, myeloma • Deficiency – vitamins B12, B1, B6 • Genetic – HSMN (Charcot-Marie Tooth), Friedrich’s Ataxia Tests Bloods to Ix cause ?Lumbar puncture (GBS/CIDP) Nerve conduction studies Treatment Neuropathic analgesia, Mx underlying cause

35. Case 6

36. O/E • Large sore tongue Lower limbs • Spastic paresis • Romberg positive, wide based gait • Bilateral Babinski sign • Loss of sensation in a stocking distribution • Absent ankle reflexes Diagnosis… Subacute Combined Degeneration of Spinal Cord

37. Case 7

38. O/E Lower limb Paraplegia, with bilateral Babinski sign Bilateral loss of pain and temp Normal JPS and vibration Diagnosis… Anterior Spinal Artery Syndrome

39. ASA Syndrome Infarction of anterior spinal artery Aetiology Aortic insufficiency Vasculitis Trauma/Neoplasia Ischaemia • Complete motor paralysis • Loss of pain and temp (STT) • Bladder & Bowel dysfunction • Dorsal columns intact

40. Case 8

41. O/E • Left ptosis • Diplopia on left and right gazes • Left eye doesn’t fully elevate • Mild facial weakness • Weakness of neck extension • Proximal muscle weakness (MRC 4-) Diagnosis… Myasthenia Gravis

42. Case 9

43. O/E • Flaccid paralysis in arms and legs • Widespread areflexia • Absent sensation in arms and legs • Evidence of sacral sparing – voluntary anal sphincter contraction • Hypotension Diagnosis… Spinal Shock