Persistent Weakness

Myopathic EMG confirms muscle disease and excludes ALS
Repetitive nerve stimulation abnormalities suggest a neuromuscular junction disorder (e.g., MG, LEMS, botulism)
CK elevation supports myopathy

May need DNA testing for further distinction of inherited myopathies

Muscle biopsy will help distinguish many disorders

ALS, amyotrophic lateral sclerosis; CK, creatinine kinase; DM, dermatomyositis; EMG, electromyography; EOMs, extraocular muscles; FSHD, facioscapulohumeral dystrophy; IBM, inclusion body myositis; IMNM, immune-mediated necrotizing myopathy; MG, myasthenia gravis; OPMD, oculopharyngeal muscular dystrophy; PM, polymyositis.

End

Patterns of Weakness on Neurologic Exam

Proximal > distal
IMNM; PM; DM; muscular dystrophies; mitochondrial and metabolic myopathies; toxic, endocrine myopathies

Ptosis, EOMs
OPMD; mitochondrial myopathy; myotubular myopathy

Facial and scapular winging
(FSHD)

Facial, distal, quadriceps; handgrip myotonia
Myotonic muscular dystrophy

Proximal & distal (hand grip), & quadriceps
IBM

Distal
Distal myopathy

Dropped head/Axial
MG; PM; ALS; hyperparathyroid; Axial myopathy