Structural lesions

 Parasagittal or foramen magnum tumors

 Cervical spondylosis

 Chiari malformation of syrinx

 Spinal cord arteriovenous malformation

Infections

 Bacterial-tetanus, Lyme

 Viral-poliomyelitis, herpes zoster

 Retroviral-myelopathy

CSF exam, culture

Lyme titer

Anti-viral antibody

HTLV-1 titers

Intoxications, physical agents

 Toxins-lead, aluminum, others

 Drugs-strychnine, phenytoin

 Electric short, x-irradiation

24-h urine for heavy metals

Serum lead level

Immunologic mechanisms

 Plasma cell dyscrasias

 Autoimmune polyradiculopathy

 Motor neuropathy with conduction block

 Paraneoplastic

 Paracarcinomatous

Complete blood count^a

Sedimentation rate^a

Total protein^a

Anti-GM1 antibodies^a

Anti-Hu antibody

MRI scan, bone marrow biopsy

Metabolic

 Hypoglycemia

 Hyperparathyroidism

 Hyperthyroidism

 Deficiency of folate, vitamin B₁₂, vitamin E

 Malabsorption

 Deficiency of copper, zinc

 Mitochondrial dysfunction

Fasting blood sugar^a

Routine chemistries including calcium^a

PTH

Thyroid function^a

Vitamin B₁₂, vitamin E, folate^a

Serum zinc, copper^a

24-h stool fat, carotene, prothrombin time

Fasting lactate, pyruvate, ammonia

Consider mtDNA

Urine and serum amino acids

CSF amino acids

Hereditary disorders

 C9orf72

 Superoxide dismutase

 TDP43

 FUS/TLS

 Androgen receptor defect (Kennedy's disease)