IM Weakness

Weakness

• DDX:
  • 1. Generalized = DO2 = CO x Hb x %Sat
    • CO = HR x SV
    • SV: preload vs. contractility
  • 2. E-lytes Ca and Na AMS while K and Mg Tone
  • 3. Myostitis vs. myopathy
  • 4. Peripheral neuro: DANG THE RAPIST (DM, Alcohol, nutrition, GB, Trauma, Hereditary, Environmental (lead),
    • Remote Ca, Autoimmune, Porphyria, Inflammation, Syphilis, TB
  • 5. Endplate
  • 6. Central lesions
• Vindicate DDX: 
  • V ascular
    
  • I nfectious
    
  • N eoplastic
    
  • D egenerative
    
  • I atrogenic/intoxication
    
  • C ongenital
    
  • A utoimmune
    
  • T raumatic
    
  • E ndocine/metabolic
• Skeletal Dx:
  • NMJ
    
    • – presynaptic cholinergic terminal
      
    • -postsynaptic motor endplate
      
  • LMN
    
    • – alpha motor neuron/cell body
      
    • – peripheral nerve
      
  • UMN
    
    • – corticospinal tract
      
    • – brainstem
      
    • -descending in the dorsolateral spinal cord
      
    • – synapse on anterior horn
• Inspect mm volume:
  • Atrophy – lesion of LMN or mm itself
• Inspect mm tone:
  • Flaccidity
    
    • – decreased tone
      
  • Rigidity
    
    • – increased tone of flexor and extensor
      
    • = extrapyramidal disturbance
      
  • Spasticity
    
    • – inc tone of either flexor or extensor
      
    • – MC UE flexor or LE extensor
      
    • = corticospinal tract disfunction
• UMN:
  • with weakness in leg extensor and arm flexor
  • weakness
    
  • spasticity
    
  • increase tendon reflex
    
  • Babinski
    
  • loss of superficial abd reflexes
    
  • little to no atrophy
• LMN:
  • weakness traceable to a single nerve
    
  • weakness
    
  • fasciculations
    
  • loss of DTR
    
  • normal abd and plantar reflexes
    
  • hypotonia
    
  • ONLY mm supplied by the involved structures are weak
• if the broad distribution of weakness:
  • NOT UMN

Myelopathy

• Etiology:
  • spinal cord disorder
    
• Causes:
  
  • Acute
    
    • – injury/trauma
      
    • – herniated disc
      
    • – infection [epidural abscess]
    • – transverse myelitis [infectious or inflammatory]
  • Subacute
    
    • – nutritional [B12, copper]
    • – infection
      
    • – transverse myelitis
      
  • Chronic
    
    • – demyelinating [multiple sclerosis]
    • – tumors
• Types:
  • central cord syndrome
    
  • anterior cord syndrome
    
  • brown sequard syndrome
    
  • complete transection of the cord
• Presentation:
  • can be unilateral or bilateral
    
  • distal weakness> proximal weakness
    
  • sensory deficits are common
    
  • spasticity
    
  • consider if
    
    • – posterior columns or spinothalamic tracts involved
• Diagnostic:
  • Xray
    
  • CT
    
  • BUT
    
    • – MRI most helpful
      
    • -use contrast if no acute injury that might cause bleeding
• Treatment:
  • corticosteroids
    
  • symptomatic tx
    
  • PT/OT

Central cord syndrome

• Etiology:
  • injury to the center of the cord
    
    • – edema, hemorrhage, syrinx formation
      
    • – usually hyperextension injury with cervical spondylosis
      
    • = weakness and sensory loss in ALL extremities
      
  • upper>lower
    
    • – will affect pain, temp, light touch, vibration, position
      
    • – neck pain and urinary retention are common

Anterior cord syndrome

• Etiology:
  • ipsilateral
    
    • – paralysis
      
    • [CST crosses at medulla]
  • contralateral
    
    • – loss of pain and temp
      
  • dorsal column is still intact

Brown-Sequard Syndrome

• Etiology:
  • hemisection of the spinal cord
    
  • ipsilateral
    
    • – paralysis
      
    • – loss of vibration, proprioception
      
  • contralateral
    
    • – pain/temp
       

Complete transection of the cord

• Etiology:
  • loss of ALL motor and sensation BELOW the level of the lesion
    
    • – will be flaccid
      
  • can also have urinary and fecal retention, bradycardia, hypotension
    
    • =spinal shock
      
    • – loss of most of spinal cord fxn
      
  • ex:
    
    • – quadriplegia
      
    • – paraplegia

Amyotropic lateral sclerosis (ALS)

• Etiology:
  • usually sporadic, some familial
    
  • – death of anterior horn cell body
• Presentation:
  • weakness of limbs
    
    • -tripping, foot drop
      
  • bulbar symptoms
    
    • – dysphagia
      
    • -dysarthria
      
  • eventually leads to
    
    • – mm atrophy
      
    • – stiffness
      
    • – loss of speech
      
    • -respiratory failure
      
  • extraocular mm and sphincters spared
    
  • associated with frontotemporal dementia
• Diagnostic:
  • EMG/NCS
    
    • – at 3 levels
      
  • MRI to r/o other things
    
    • – CSF is normal
• Treatment:
  • mostly supportive
    
  • riluzole
    
    • – glutamate antagonist
      
  • edaravone
    
    • – free radical scavenger
      
  • why is hard to cure?
    
    • -dz is sudden with no cause

Infectious anterior horn

• Polio
  
  • –fecal/oral
    
  • – fever, malaise followed by myalgia
    
  • -asymmetric weakness
    
  • -tx supportively
    
• West Nile virus
  
  • – usually meningoencephalitis
    
  • – asymmetric weakness
    
  • OR
    
  • – rapid ascending quadriplegia
    
  • – dx by CSF and EMG
    
  • – tx supportively

Polymyositis

• Etiology:
  • after 20
    
  • no familial cause
    
  • weeks to mom
    
• Physical Exam: 
  • Generalized + dysphagia
    
• Diagnostic: 
  • CK, ESR
    
• Management: 
  • steroids

Dermatomyositis

• Etiology:
  • no age
    
  • 10% lung, breast, GI
  • rash and weakness to achy
  • Common rash sites:
    • knuckles, knees, elbows,(extensors) eyelids, face

Muscular dystrophy

• Etiology:
  • group of hereditary diseases characterized by degeneration of muscle and weakness

Myotonic Dystrophy

• Etiology:
  • AD, CTG repeat in 19th chrome
    
  • chronic
    
• Presentation:
  
  • Swallow/face weakness and DISTAL weakness
    
  • balding, retarded, cataracts, gonad atrophy, arrhythmia, stiff in cold
• Diagnostic: 
  • we really don’t need genetic testing with Fam Hx, still do EMG 
    
  • EMG – myotonic discharges
• Management: 
  • pacemaker, eye surgery,
  • Medication:
    • phenytoin, quinidine, procainamide for myotonia

Myopathy

• 4 indications of myopathy:
  • proximal
    
  • getting out of the chair, climbing stairs, lifting arms overhead
• Cause of myopathy:
  • vascular
    
  • HIV infection
    
  • alcohol toxin
    
  • drugs
    
  • thyroid
• Drugs that kill muscle (Anti- GLAS):
  • steroids
    
  • anti-lipid agents
    
  • anti gout
    
  • amiodarone

Acute inflammatory demyelinating polyneuropathy

• Etiology:
  • Post-viral Schwann attack
    
  • 2-4 weeks
    
• Physical Exam: 
  • GSE loss, maybe some paresthesias (numb, burn, tingle)
    
  • areflexic
    
• Work-Up:
  • EMG and NCS and lumbar puncture
    
  • denervation or conduction block
    
  • High protein with NO CELLS in the cistern
• Treatment:
  • monitor respirations for intubations, IVIG/plasmapheresis

Myasthenia Gravis

• Etiology:
  • thymoma
    
  • 30% of ACh receptors left
    
• Presentation:
  • Dysarthria, dysphonia, dysphagia, dyspnea (CN), limb and neck weakness
• Diagnosis:
  • Ach:
    • 50% ocular MG
      
    • 90% generalized
  • Ab, EMG, and NCV, fatigue with repetition
  • Chest CT for thymoma
• Medications that exacerbate Myasthenia gravis (MAPMAN):
  • Mg
    
  • Antibiotics
    
  • penicillamine
    
  • Muscle relaxers
    
  • anesthetics
    
  • narcotics
• Management:
  • Rest test, Ice test, edrophonium
  • Pyridostigmine, neostigmine, IVIG, steroids, azathioprine, cyclophosphamide, Cellcept, thymectomy
    
  • PN-SACC

Lambert Eaton

• Etiology:
  • -low ACh release due to Ca Channel presynaptic terminal dysfunction
    
  • -paraneoplastic syndromes
    
  • -LE>UE
    
  • -more ANS dysfunction(dry mouth) less respiratory
  • get stronger with repetition
• Treatment:
  • treat cancers
    
  • IVIG
    
  • prednisone
    
  • azathioprine