Board Review- Neuromuscular Disorders

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

(B) Humans have 2 primary types of muscle fiber (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.

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

C: XP 21 X-linked recessive

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.

(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.

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.

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

ALS typically affects males or females more predominantly?

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

Upper motor neuron signs at the time of diagnosis. 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.

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.

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.

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.

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

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.

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

(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.

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

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.

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

B. Likely due to mechanical joint fatigue and overuse 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.

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

B. typical changes of post polio foot include skin changes, lymphedema 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.

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.

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.

The patient in the picture above is seen in the outpatient clinic 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.

C: FSH muscular dystrophy

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

C) CMT-1 ONION BULB FORMATION

SMA-1 patients never could sit 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.

C: SMA-1 patient’s never gained the ability to sit. Fairborn A 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.

Kugelberg Welander, SMA-2, Werdnig Hoffman 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.

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 IV This form of SMA affects adults in their 30s and 40s, resulting in a walking disability.

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

A) Vincristine

b) Nonsteroidal anti-inflammatory medications c) Tylenol 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.

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.

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

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.

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

E: EtOH causes 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.

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.

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 .

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.

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

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

C: **If the active and reference electrodes are placed less than 3 – 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**

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

B) Myotonic discharges are single fiber discharges that wax and wane in frequency and amplitude.

Which potentials have manifestations that CANNOT be observed on physical examination? (a) Fasciculation potentials (b) Myokymic discharges (c) Complex repetitive discharges (d) Cramp potentials

C: CRDs can only be detected with EMG C: CRDs can only be detected with EMG. The remainder of the discharges have manifestations that can be observed on physical exam

Which neuromuscular disorder is NOT usually associated with thyroid disease? A. peripheral neuropathy B. neuromuscular junction disorder C. Myopathy D. Radiculopathy

D. Thyroid disease is associated with several different aspects of the neuromuscular system. In both hypothyroidism and hyperthyroidism, there can be neuromuscular junction disorders (myasthenia), and myopathy. Hypothyroidism is associated with sensorimotor peripheral neuropathy and entrapment neuropathy, especially carpal tunnel syndrome. Thyroid disease is not associated with radiculopathy.

What condition casues the typical “myopathic gait” seen in a young boy with Duchenne muscular dystrophy with accentuated lumbar lordosis and toe walking? (a) Hip and knee extensor weakness (b) Hip flexion and ankle plantar flexion contractures (c) Hip extensor weakness and plantar flexion contracture (d) Hip flexion contracture and knee extensor weakness

A) Hip and knee extensor weakness

Factors associated with poor prognosis in multiple sclerosis include (a) female gender. (b) age at onset less than 20 years. (c) cerebellar involvement at onset. (d) relapsing remitting course at onset.

C: Patients have a poor prognosis if they are male, >35 y/o, polysymptomatic, rapidly progressive, motor symptoms, ataxia, tremor, high rate of relapse

Which of the following neuropathies has the slowest conduction velocity? A. dejerine sottas B. friedreich’s ataxia C. fabry’s disease D. CMT type 1 E. CMT type 2

A. Dejerine Sottas: CV is usually less than 10 m/s

MS patients experience a marked sensitivity to heat. This is called: A. Lhermitte’s sign B. Uhthoff’s phenomenon C. Hoffman’s sign D. Kennedy phenomenon

B. Uhthoff’s phenomenon

All of the following diseases may present with ptosis except: A. Myasthenia Gravis B. Botulism C. Myotonic Dystrophy D. Fascioscapulohumeral dystrophy

D. Fascioscapulohumeral dystrophy In FSH, the extraocular muscles are spared

A patient having difficulty late in the day getting up from a chair, going up or down stairs, and reaching with his arms presents for electrodiagnostic studies. Physical exam demonstrates normal DTRs and normal findings on manual muscle testing. Standard sensory and motornerve conduction studies are normal. Repetitive axillary nerve stimulation (RNS) performed at 2Hz demonstrates 20% decremental response. Immediately after exercise, the RNS decrement is no longer observed. Three minutes following exercise, however, the decrement is greater. Needle EMG results are normal. (SAE)

Upon further investigation, you would most likely find what additional clinical finding? (a) Asthma (b) Dry mouth (c) Ptosis (d) Skin rash

C. Ptosis The patient presents with myasthenia gravis (MG), a postsynaptic neuromuscular junction disorder. Ptosis and extraocular weakness often occur in MG. Lambert-Eaton myasthenic syndrome (LEMS), a presynaptic neuromuscular junction disorder, would demonstrate postexercise facilitation (at least 100% increase in first response CMAP immediately following exercise) and likely have low-amplitude baseline CMAP results. Autonomic symptoms such as dry mouth often accompany LEMS.

Long-term steroid treatment for asthma may cause myopathy without significant needle EMG results, but RNS would be normal. Although dermatomyositis typically presents with proximal weakness, no abnormalities characteristic of an inflammatory myopathy were seen on needle electromyography.

Which muscle group displays the earliest pattern of weakness in Duchenne muscular dystrophy? A. Ankle dorsiflexors B. Neck flexors C. Shoulder flexors D. Knee extensors (SAE)

B. Neck flexors In Duchenne muscular dystrophy, weakness is first seen in the neck flexors during preschool years. Pelvic girdle weakness precedes shoulder girdle weakness by several years. Ankle dorsiflexors are weaker than plantarflexors; ankle everters are weaker than inverters; knee extensors are weaker than flexors; hip extensors are weaker than flexors.

A. No effect on the onset latency of the CMAP In performing motor nerve conduction studies, what is the effect on the compound muscle action potential (CMAP) of placing the recording electrodes (active and reference) closer together, over the same muscle? A. No effect on the onset latency of the CMAP B. An increase on the CMAP amplitude C. A prolongation of the peak latency D. A decrease in the calculated conduction velocity (SAE)

A. No effect on the onset latency of the CMAP If the active and reference electrodes are placed too close together, similar waveforms will be recorded on both sites and these waveforms will be rejected. This will result in an CMAP amplitude drop. There is no effect on the onset latency.

What feature is suggestive of polymyositis? A. Distal symmetric weakness without pain B. Reduced motor nerve conduction velocities and conduction block C. Electromyography with low voltage, polyphasic potentials D. Brisk tendon reflexes (SAE)

C. Electromyography with low voltage, polyphasic potentials

Cognitive deficits are common in A. Duchenne muscular dystrophy B. Inclusion body myositis C. Fascioscapulohumeral dystrophy D. Becker muscular dystrophy (SAE)

A. Duchenne muscular dystrophy Brain isoform of dystrophin exists and there are documented mildly decreased Intelligence Quotient scores in people with Duchenne muscular dystrophy. These lower scores may be specific to deficits with tasks requiring attention to complex verbal information.

All hereditary sensory motor neuropathies are characterized by: A. Decreased intelligent quotient scores B. Spinal deformities C. Muscle weakness D. Joint contractures (SAE)

C. Muscle weakness The residual muscle force in the later stages of the disease is 20-30% of normal. Intelligence quotient reduction, significant joint contractures, pulmonary/cardiac abnormalities and spinal deformities are not typical of HSMN.

Which symptom is most predictive of cardiac disease in Duchenne muscular dystrophy? A. Palpitations B. Syncope C. Dyspnea D. Cachexia (SAE)

C. Dyspnea The most frequent predictive symptom is dyspnea. Absence of exertion dyspnea from lack of physical activity allows myocardial impairments to remain clinically silent and difficult to detect. A high index of suspicion is required. Electrocdardiogram abnormalities in both Duchenne and Becker muscular dystrophy patients are attributed to progressive fibrosis of the cardiac conduction system and impairment in the cardiac autonomous nervous system. Palpitations and syncope will be related to the conduction abnormalities and occurs late in the disease process.

Cachexia is a late finding that occurs when feeding becomes difficult as a result of heart failure and dyspnea

C. Severe proximal weakness D. Mild mental retardation A prominent feature of the most common form of Charcot–Marie-Tooth disease is: A. Truncal ataxia B. Sensory impairment C. Severe proximal weakness D. Mild mental retardation (SAE)

B. Sensory impairment

A 36 year-old man has a known history of HIV A 36 year-old man has a known history of HIV. His family has observed worsening confusion and memory loss. He later develops progressive paraparesis, ataxia, posterior column sensory loss, and neurogenic bowel and bladder. The most likely diagnosis is: A. Viral myelitis B. Multiple sclerosis C. Cytomegalovirus (CMV) polyradiculopathy D. Vacuolar myelopathy (SAE)

D. Vacuolar myelopathy Vacuolar myelopathy is the most common cause of spinal cord dysfunction in (HIV) patients, being found in 11% to 22% of acquired immunodeficiency disease (AIDS) cases, and demonstrable in as many as 40% of cases at autopsy. It is strongly associated with HIV dementia, and shares a virtually identical histopathology. The other diagnoses are less common, and can be ruled out or in with imaging, laboratory and electrodiagnostic studies.

A 40-year-old woman is currently hospitalized for a severe flare of her polymyositis. On consultation, you recommend that while in the hospital she begin: (a) passive range-of-motion exercises to prevent contractures. (b) isometric strengthening exercises at the bedside to maintain her strength. (c) ambulation with a walker in the hallways supervised by her therapist. (d) strengthening exercises with light hand and ankle weights. (SAE)

(a) passive range-of-motion exercises to prevent contractures. Passive range of motion to maintain joint movement is recommended during periods of acute flares. With resolution of the flare, active-assisted exercises may be started, progressing to strengthening exercises and ambulation.

Which statement regarding glossopharyngeal breathing is TRUE? A. It is typically useful in patients with weak oropharyngeal muscles B. It is recommended therapy in a patient with laryngeal cancer C. It is generally used when a patient has a tracheostomy D. It is a useful backup for any mechanical failure of ventilatory assistance (SAE)

D. It is a useful backup for any mechanical failure of ventilatory assistance