Common Causes of Weakness | |||
| Upper Motor Neuron | |||
| Cortex: Ischemia; hemorrhage; intrinsic mass lesion (primary or metastatic cancer, abscess); extrinsic mass lesion (subdural hematoma); degenerative (amyotrophic lateral sclerosis) | |||
| Subcortical white matter/internal capsule: Ischemia; hemorrhage; intrinsic mass lesion (primary or metastatic cancer, abscess); immunologic (multiple sclerosis); infectious (progressive multifocal leukoencephalopathy) | |||
| Brainstem: Ischemia, immunologic (multiple sclerosis) | |||
| Spinal cord: Extrinsic compression (cervical spondylosis, metastatic cancer, epidural abscess); immunologic (multiple sclerosis, transverse myelitis); infectious (AIDS-associated myelopathy, HTLV-I-associated myelopathy, tabes dorsalis); nutritional deficiency (subacute combined degeneration) | |||
| Motor Unit | |||
| Spinal motor neuron: Degenerative (amyotrophic lateral sclerosis), infectious (poliomyelitis) | |||
| Spinal root: Compressive (degenerative disk disease); immunologic (Guillain-Barré syndrome); infectious (AIDS-associated polyradiculopathy, Lyme disease) | |||
| Peripheral nerve: Metabolic (diabetes mellitus, uremia, porphyria); toxic (ethanol, heavy metals, many drugs, diphtheria); nutritional (B12 deficiency); inflammatory (polyarteritis nodosa); hereditary (Charcot-Marie-Tooth); immunologic (paraneoplastic, paraproteinemia); infectious (AIDS-associated polyneuropathies and mononeuritis multiplex); compressive (entrapment) | |||
| Neuromuscular junction: Immunologic (myasthenia gravis); toxic (botulism, aminoglycosides) | |||
| Muscle: Inflammatory (polymyositis, inclusion body myositis); degenerative (muscular dystrophy); toxic (glucocorticoids, ethanol, AZT); infectious (trichinosis); metabolic (hypothyroid, periodic paralyses); congenital (central core disease) |
Abbreviation: AZT, azidothymidine.