Neuromuscular Diseases Lecture Powerpoint Flashcards
Neuromuscular disease definition and most common symptom
- Disease that affects function of muscles due to problems with the nerves and muscles
- Most common symptom is muscle weakness (not general weakness but physical muscle weakness)
Myasthenia gravis
Most common neuromuscular transmission disorder, typically acquired by immunological abnormality but sometimes genetic, disorder of post synaptic neuromuscular junction
Pathophysiology of myasthenia gravis
- Post synaptic muscle membrane becomes distorted and simplified (loses its normal folded shape)
- This prevents Ach from binding to its receptors properly at the muscle end plate (alongside autoantibodies attaching to the membrane)
Myasthenia gravis most common onset age in women vs men
Women in 2nd to 3rd decade of life, men in 7th to 8th
Thymus-myasthenia gravis relationship
Many patients with myasthenia gravis have an enlarged thymus (not diagnostic, just a trend - can see enlaraged thymus for a variety of reasons), often triggers and maintains the production of antibodies that block the acetycholine
Myasthenia gravis presentation and 2 co-occurring symptoms in some cases
Fluctuating fatigable specific muscle weakness that worsens with activity and improves with rest, often worsening as the day progresses, with prolonged muscle use, with hot temps, stress, or infection. Most often begins with weakness of eye muscles, difficulty swallowing, or slurred speech with initial transient symptoms that gets worst within 1 year
-2/3 also have co-occurring ocular disturbances such as ptosis or ocular muscle weakness OR 1/6 have oropharyngeal muscle weakness (difficulty swallowing or talking)
Bulbar area of brain
Cerebellum, medulla, and pons including CN IX, X, XI, and XII
2 types of myasthenia gravis
- occular
- generalized
Myasthenia gravis diagnostic tests (5)
- Aceycholine receptor antibodies (80% of the time diagnostic)
- if negative then check muscle specific receptor tyrosine kinase (MuSK)
- Tensilon (edrophonium) test that blocks breakdown of Ach
- EMG:electromyogram to assess nerve and msucle function
- Ice pack test, cold decreases breakdown of Ach at the neuromusclar junction resulting in decreased ptosis
Myasthenia gravis treatment options (5), are any curative?
- Pyridostigmine (mestinon) that increases Ach available
- Immunotherapeutic agents such as prednisone or cyclosporine
- Plasmapheresis (replace antibody containing plasma with antibody free plasma)
- IV immunoglobulin
- Thymectomy
-(NONE of these are curative, only helpful)
Amyotrophic lateral sclerosis (ALS) AKA Lou Gehrig’s disease
Progressive incurable disease that affects nerve cells of the brain and spinal cord causing loss of muscle control resulting in muscle weakness, disability, and death with a median survival of 3 years
ALS epidemiology
Slight male predominance for sporadic cases, ALS is sporadic in 90-95% of cases, inherited in 5-10% of patients, increased risk suggested in laborers or military
ALS pathophysiology
Nerve cells that control volutnary muscle movements are affected, motor neurons gradually deteriorate and therefore are unable to send signals to muscles, theorized to be due to a complex interaction between environmental and genetic factors
ALS clinical findings in upper motor neurons and lower (3 in each)
Upper motor neuron findings (slow speech, jaw jerk, spasticity)
Lower motor neuron findings (atrophy, fasciculations, weakness)
ALS presentstion
Most common presentation in 80% is asymmetric limb weakness, 20% have onset in the bulbar segment resulting in dysarthria and dysphagia
Dysarthria
Weakness of muscles used for speech resulting in slowed or slurred speech
ALS signs and symptoms (7)
- Difficulty walking
- Tripping
- Weakness in hands, legs, and feet (foot drop)
- slurred speech or trouble swallowing
- muscle cramps
- inappropriate crying, yawning, laughing
- cognitive or behavioral changes
ALS often starts in the ____ and spreads to ____.
Does it cause pain? What system is not affected?
hands/feet/limbs, chewing/swallowing/speaking, does not cause pain in any stage, sensation and bladder control typically not affected
ALS diagnostic criteria (3)
- Upper and lower motor signs
- progressive clinical course
- lack of other etiology
ALS diagnostic tests (3)
- EMG
- Nerve conduction study
- MRI
ALS prognosis
Time from symptoms onset to typical diagnosis is 14 months, mean survival is 30 months, 30% survival 5 years after diagnosis, significant variability in rate of progression and requires palliative care from onset
ALS treatment options (4)
- Riluzole (rilutek) oral increases life expectancy 3-6 months
- Edaravone (radicava) IV infusion
- Meds to manage symptoms
- Therapies such as physical, occupational, nutritional, etc
ALS management
Encouraged to have a pre-determined plan before loss of functionality such as respiratory failure or nutritional failure to determine what they will do
Muscular dystrophy
Group of diseases that cause progressive weakness and loss of muscle mass, has no cure but meds and therapies can manage symptoms with signs and symptoms beginning at diff ages and diff muscle groups, often due to abnormal genes interfering with production of proteins to form healthy muscle
Signs/symptoms of muscular dystrophy (1)
-Main one is progressive muscle weakness
Duchenne muscular dystrophy (etiology and presentation)
Most common form of musclular dystrophy that is X linked recessive (more common in boys)
Often seen in 2nd year of life with early clumsiness walking
Gower’s maneuver
Refers to a common finding in duchenne muscular dystrophy where a patient has to place 1 hand on knee to assume upright position because of ilitibial bands and heel cords become tight
Duchenne muscular dystrophy progression (3)
- By 5-6 stair climbing becomes labored
- 6-7 frequently falls
- 8-10 cease to be able to climb stairs or stand from floor often requiring wheel chair
Cardiac, growth, and orthopedic complications from duchenne muscular dystropy
- primary dilated cardiomyopathy and conduction abnormalities resulting in degeneration and fibrosis
- short stature and growth delay
- fractures from frequent falling
Duchenne muscular dystrophy pathophysiology
Caused by mutation of gene that encodes dystrophin that helps keep muscles intact (protein localized to inner surface of sarcolemma of muscle fiber) affecting proximal muscles first then distal
Duchenne muscular dystrophy visual inspection findings
Thick lower leg muscles due to fat not muscle, thin weak thighs especially in front, weak muscles in front of leg cause foot drop and tiptoe contractures, belly sticks out due to weak muscles, shoulders and arms held back when walking
Duchenne muscular dystrophy diagnosis (4)
- DNA studies looking for deletion of dystrophin gene, 30% of patients are negative then
- muscle biopsy is required to establish absence of dystrophin
- Serum CPK levels markedly elevated
- EMG sees myopathic changes
Duchenne muscular dystrophy treatment (4)
- PT to keep joints loose as possible and maintain ligament laxity
- night splints and braces can delay progression
- surgery such as reconstruction or tendon release
- prednisolone
Duchenne muscular dystrophy prognosis
-16-18 predisposed to fatal pulmonary infections, affected children die from respiratory failure or cardiomyopathy that is resistant to treatment, or aspiration and acute gastric dilation
Becker muscular dystrophy differences from Duchenne
Signs and symptoms similar to duchenne but tends to develop more slowly in teens and be more mild perhaps not occurring until mid 20’s or later
Cerebral palsy
Group of disorders that affects muscle tone or posture and movement, can range in severity, caused by damage (such as lack of oxygen) to immature brain as it develops most often before birth, most common motor disability in childhood (4/1000) signs and symptoms appear during infancy or preschool years
Cerebral palsy causes prenatal (3) and natal (3) and what % does prenatal vs natal be seen as the cause
Prenatal: (70%), infection, anoxia, toxicity
Natal: (5-10%), anoxia, traumatic delivery, metabolic dz
Cerebral palsy risk factors (4)
- alcohol consumption
- prematurity
- intrauterine growth restriction or infection
- antepartum hemorrhage
4 origin types of cerebral palsy and what determines it
- spastic
- dyskinetic
- ataxic
- mixed
-Based on what part of brain has damage
Cerebral palsy signs and symptoms
-vary but all have problems with movement and posture, some may have intellectual disability, visual or hearing defect, etc.
Different types of cerebral palsy and what they mean (6)
- monoplegic (1 extremity)
- paraplegic (2 lower extremities)
- Hemiplegic (1 side upper and lower extremities)
- Triplegic (3 extremities)
- Quadraplegic (4 extremities)
- Diplegic (symmetrical left and right either upper or lower extremities)
Cerebral palsy diagnosis
-Clinical based on risk factors around birth, ruling out other etiologies, and relying on developmental milestones
Cerebral palsy treatment (3)
- physical therapy
- occupational therapy
- pharmacologic intervention to reduce symptoms that impair muscle coordination and control
Myasthenia gravis lifestyle modifications (2)
- Avoid overexertion
- Eat foods high in potassium to help maintain muscle strength
Fasciculation
Small, local, involunary muscle twitch
Cerebral palsy diagnostic studies (3)
Performed by ruling out other etiologies via
-MRI
-Cranial ultrasound
EEG
