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 examination, 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

Superoxide dismutase

TDP43

FUS/TLS

Androgen receptor defect (Kennedy's disease)

Hexosaminidase deficiency

Infantile a-glucosidase deficiency (Pompe's disease)