Board Review- Neuromuscular Disorders

1. Board Review- Neuromuscular Disorders

2. Which muscle fiber is characterized by fast-twitch oxidative metabolic properties? • (a) Type 1 • (b) Type 2a • (c) Type 2b • (d) Type 3

3. (B) Humans have 2 primary types of muscle fiber. They are divided according to many different characteristics, including speed of contraction and sources of fuel. Type 1 muscle fibers are slow-twitch with oxidative metabolic pathways. Type 2 muscle fibers are fast-twitch fibers. The type 2 fibers can then be further divided into fast-twitch oxidative (type 2a) and fast-twitch glyclolytic (type 2b). There are no muscle fibers designated as type 3.

4. Duchenne/Becker muscular dystrophy is a defect within codes 4 dystrophy molecule located: • XP 11 • XP 16 • XP 21 • XP 18

5. C: XP 21 X-linked recessive

6. Which one of the following characteristics is typically associated with Charcot Marie Tooth (CMT) disease type 2? • (a) minimal level of disability. • (b) minimal decrease in nerve conduction velocity. • (c) autosomal recessive inheritance. • (d) absence of sensory deficits.

7. (B) minimal decrease in nerve conduction velocity. • Charcot Marie Tooth (CMT) disease type 2 has greater variability and produces more disability than type 1. The disability can range from very mild to severe in CMT type 2. In addition to the weakness typical of the hereditary sensory motor neuropathy diseases, paresis of diaphragm, vocal cord, and intercostal muscle has been reported. CMT type 2 disease is characterized by less hypertrophic change in myelin, with more neuronal or axonal involvement. Sensory deficits are common to both forms. Both have autosomal dominant inheritance.

8. All of the following is true about ALS except: • Characterized by progressive degeneration and loss of motor neurons and cortex, brain stem and spinal cord. • Spares bulbar function • Affects respiratory and limb musculature. • Results in both upper motor neuron and lower motor neuron signs.

9. B. Spares bulbar function • ALS does affect cranial nerves (bulbar function)

10. ALS typically affects males or females more predominantly? • Males • Females

11. A: Males 1.5-2.0:1 ratio approaching 1:1 with increasing age over 70. Remember: Lou Gehrig !

12. All of the following suggest a poor prognosis of the ALS patient except: • Upper motor neuron signs at the time of diagnosis. • Short duration of time from onset of symptoms. • Older age of onset • Bulbar dysfunction early in disease course. • Pulmonary dysfunction early in disease course.

13. A: Upper motor neuron signs at the time of diagnosis. • Typically it is lower motor neuron signs at the time of diagnosis not upper motor neuron signs to suggest a poor prognosis. • REVIEW: POOR PROGNOSIS = • Older age at time of onset • Bulbar dysfunction early in disease course • Pulmonary dysfunction early in disease course • Short period of time from onset of symptoms to diagnosis. • Lower motor neuron signs at the time of diagnosis.

14. All of the following needle EMG findings in LMN dysfunction in ALS patients would be suspected except Increased MUAP amplitude, increased duration and polyphasic potentials. Decreased MUAP amplitude, short duration, polyphasic potentials. myotonic discharges Increased jitter single fiber needle EMG.

15. A: You’d expect a neuropathic pattern on needle EMG : • Increased MUAP amplitude, increased duration, decreased recruitment, polyphasic potentials. • Denervation potentials (fibrillations and positive sharp waves) would also be expected. • Jitter on single fiber EMG is more suggestive of myasthenia gravis. • Decreased MUAP amplitude, decreased duration is more suggestive of myopathies.

16. 72-year-old Caucasian male with PMH of hypertension, atrial fibrillation, BPH, aggressive weakness and functional disability from advancing ALS. Now progressive swallowing dysfunction and sialorrhea. He decided to manage his sialorrhea and the best choice would be? Amitriptyline Scopolamine Bethenachol Botox parotid gland injection

17. D: Botox parotid gland injection Anticholinergic medications have a relative contraindication in patients with glaucoma, BPH, and cardiac conduction disorders. Botox would probably be an excellent choice in this case.

18. A 70-year-old man presents with a 3-month history of numbness in patchy areas over the limbs and torso. His numbness began in the left foot, then the right hand, followed by numbness over the back and all the limbs. He has no complaints of bowel or bladder problems. He has a long history of smoking. His examination reveals normal strength, normal cranial nerve function, but sensation is decreased to pin prick, vibration, and position in the limbs. Deep tendon reflexes are absent. Electrophysiologic studies show normal motor nerve conduction and needle examination of the upper and lower limb muscles. The sensory nerve conduction studies show small or absent responses. Based on this information what test would you order next? • (a) Nerve and muscle biopsies • (b) Radiologic studies to assess for a tumor • (c) Skin biopsy to assess small nerve fibers • (d) Repetitive nerve conduction studies

19. (B) The clinical and electrophysiologic presentation is consistent with a sensory neuropathy. With no evidence to suggest motor involvement, the numbness is likely a disorder of the dorsal root ganglion. There are only a few distinct disorders associated with acute or subacute cases described by the history and physical in this clinical vignette. They may be part of a paraneoplastic syndrome, connective tissue disorder such as Sjogren’s, a post infectious condition, pyridoxine intoxication, or as an isolated autoimmune process. In this patient with a history of smoking, a cancer work up would include obtaining anatomic studies of the chest. Biopsies of the nerve, muscle, or skin would not add much to the case. Repetitive nerve conduction studies would be considered if a neuromuscular junction disorder was suspected.

20. Which are the typical histologic characteristics of patients with post polio syndrome. Motor units are 7-8 times larger. High PMN’s count found surrounding sarcolemma. Muscle biopsy shows frequent, isolated, atrophic fibers rather than groups of atrophic fibers. Fiber type grouping A & C B & D All of the above

21. E: A & C: • Histologic evidence indicates motor units are 7-8 times larger than normal due to ongoing denervation & reinnervation. Over time, denervation becomes permanent. Muscle biopsy shows frequent isolated atrophic fibers rather than groups of atrophic fibers.

22. Post polio muscle pain is thought to be secondary to: Persistent muscle spasticity Likely due to mechanical joint fatigue and overuse. Neuropathic pain from spinal cord neuron damage. Inflammatory myopathy

23. B. Likely due to mechanical joint fatigue and overuse. Post polio muscle pain characterized often by superficial burning, cramping and tired feeling or a deep muscle ache commonly occurs with muscle overuse. Is likely due to muscle strain, fatigue and overuse of the joint and muscle. Usually it occurs at night or after activity. Neuropathic pain in PPS can occur but typically from entrapment neuropathies such as CTS or radiculopathy rather than spinal cord neuron damage.

24. The “polio foot” is characterized by the following: Atrophy, foot drop Lymphedema Erythema and burning foot pain. Ankle contracture/soft tissue contracture

25. B. typical changes of post polio foot include skin changes, lymphedema. Secondary to polio vascular beds in the limb have not developed normally and lymphedema ensues.

26. All of the following are true about the use of steroids in the treatment of Duchenne muscular dystrophy except: • Steroids are the only pharmaceutical palliative treatment available for Duchenne • Prolongs motor function • Reducing risk of scoliosis progression • Does not cause the problems of weight gain typically seen in the adult patient.

27. D: steroids do in fact cause weight gain. The steroids used in Duchenne muscular dystrophy is in fact the only pharmaceutical palliative treatment for Duchenne. It is not universally used. He does prolong motor function however there is a high incidence of side effects specifically weight gain and osteoporosis.

28. The patient in the picture above is seen in the outpatient clinic. Based on inspection respected physical diagnosis would be? • Disuse atrophy and weakness of the rhomboids and trapezius. • Polyneuropathy especially affecting long thoracic nerve and dorsal scapular nerves. • FSH muscular dystrophy • bilateral frozen shoulder with scapulohumeral disassociation.

29. C: FSH muscular dystrophy

30. Q: A patient with weakness in lower extremities has a sural nerve biopsy. Diagnosis based on biopsy? Peripheral neuropathy Werdnig Hoffman CMT-1 Inflammatory myopathy

31. C) CMT-1 ONION BULB FORMATION

32. Spinal muscular atrophy is characterized by selective destruction of the anterior horn cells. SMA-1 and SMA-2 had similar effects and presentation. The primary difference between the two is: • Findings on biopsy consisting of both hypertrophic and atrophic fibers. • Findings on EMG/MCV • SMA-1 patients never could sit • SMA-1 in the pediatric onset, SMA-2 is adult onset.

33. C: SMA-1 patient’s never gained the ability to sit. Fairborn A. “floppy infant” whereas SMA 2 patient’s onset is 2-12 and therefore may be sitting and walking prior to onset.

34. What is the correct chronologic order that the following SMA syndromes occur based on onset of disease? • Kugelberg Welander, SMA-2, Werdnig Hoffman • SMA-2, Werdnig Hoffman, Kugelberg Welander • Werdnig Hoffman, SMA-2, Kugelberg Welander • None are correct since two of these syndromes are not SMA syndromes.

35. C: Werdnig-Hoffman, SMA 2, Kugelberg-Welander • type I (Also called Werdnig-Hoffman.)This is the most severe type of SMA and may be present at birth. Infants have problems holding their head, sucking, feeding, swallowing, and typically move very little. The muscles of the chest are also affected. The motion of the tongue is described as having "worm-like" movements. Death results usually by the age of two to six years from breathing problems. • type II (intermediate form)This form of SMA is seen in children from seven months to 18 months of age. They typically have generalized muscle weakness and may require braces, walkers, or a wheelchair for assistance. Life-expectancy may extend to the 20s and 30s. • type III (Also called Kugelberg-Welander.)This form of SMA affects children older than 18 months of age. These children show signs of clumsiness, difficulty walking, mild muscle weakness, and may be developmentally delayed. These children live long into their adult years. • type IVThis form of SMA affects adults in their 30s and 40s, resulting in a walking disability.

36. Which medication causes axonal neuropathy most frequently? • A) Vincristine • B) Vinblastine • C) Cisplatin • D) cyclophosphamide

37. A) Vincristine

38. A Duchenne’s muscular dystrophy patient has been describing morning headaches to his parents. On routine follow-up appointment you recommend for this complaint: a) MRI of brain b) Nonsteroidal anti-inflammatory medications c) Tylenol d) Sleep study e) Pulmonary function tests to rule out hypoventilation.

39. D) Sleep study: • Morning headaches may be a sign of sleep apnea. A sleep study may be more appropriate. Although pulmonary function tests are important for monitoring of Duchenne patient’s in this case you need to rule out sleep apnea.

40. All of the following myopathic conditions would typically demonstrate negative EMG except: • Myophosphorylase deficiency • Steroid myopathy • Hyperthyroid myopathy • Inclusion body myositis

41. D: inclusion body myositis are a group of inflammatory myopathies with MUAP and denervation potentials. Remember, endocrine myopathies and storage disease myopathies typically have abnormal EMG.

42. Which of the following potential neurotoxic agents cause axonal neuropathy? • Amiodarone • Arsenic • Gold • Tacrolimus • EtOH

43. E: EtOHcauses a typical axonal loss pattern with reduced SNAP and CMAP amplitudes. Neuropathies typically affect the legs >arms. • Women her more susceptible to neuropathy secondary to EtOH • Substances the cause demyelinating disease include: N- hexane, Suramin, amiodarone, chloroquine, cytosine arabinoside, tacrolimus, procainamide, goals, arsenic. The rest cause typically more axonal disease.

44. You are called to the ICU for a electrodiagnostic consultation to rule out critical illness polyneuropathy. The patient has failed weaning from the ventilator. She is on external pacing, she is on heparin for anticoagulation. The pulmonologist asks you to clarify whether or not the NCV can be done with the patient on pacemaker. The following is the most appropriate response: EMG/NCV can be done on patient’s with pacemaker so long as is not done vicinity of the pacemaker. EMG/NCV is contraindicated in this case. EMG/NCV can be safely done without complications or precautions on patients with pacemakers. Call the neurologist, maybe there crazy enough to do it.

45. B: EMG/NCV is contraindicated. Why? • Because this patient has an external pacemaker and not an internal pacemaker. Patient with an external pacemaker should not have NCV testing. • AANEM recommends with implanted pacemakers there is little risk of harm to the patient with a pacemaker when performing NCVS testing unless you stimulate near the brachial plexus ipsilateral to the pacemaker .

46. Which of the following statements is true regarding needle EMG studies? • There is no contraindication to needle EMG in patients with prosthetic joints when sterile single use EMG needles are used • Prophylactic antibiotics are required with significant heart valve disease prior to the EMG / NCVS procedure • There is no significant concerns performing needle EMG and patients with lymphedema. • EMG NCV studies are contraindicated in pregnancy.

47. A: There is no contraindication to needle EMG in patients with prosthetic joints when sterile single use EMG needles are used

48. What effect is having the active and reference electrodes closer than 3-4 cm apart? Increased SNAP amplitude Increased SNAP dispersion Decreased SNAP amplitudes This measurement will not matter as he will obtain the same values

49. C: **If the active and reference electrodes are placed less than3 – 4 cm apart when performing a sensory conduction, then both electrodes will record similar information which is then canceled out leading to a decrease in the value for the SNAP amplitude**

50. The potentials above are: (a) complex repetitive discharges. (b) myotonic discharges. (c) neuromyotonia. (d) myokymia.