Version July 2025
| Toxin | Etiology | Symptoms/signs | MRI | Diagnostic tests | Treatment (adult dosing) |
| Nitrous oxide | Inactivation of vitamin B12 by nitrous oxide used as anesthetic gas or whippets (recreational use of aerosol used in dispensing whipped cream) | Subacute combined degeneration of spinal cord beginning with sensory ataxia (positive Romberg sign, pseudoathetosis) followed by pyramidal symptoms and signs, with or without peripheral axonal neuropathy | T2 hyperintensity in posterior columns with inverted V sign; may extend over several levels in cervical or thoracic cord | Low serum cobalamin, high plasma methylmalonic acid, high plasma homocysteine | IM or deep SQ cyanocobalamin 1000 mcg once daily for 5 days followed by IM or deep SQ 1000 mcg once monthly indefinitely; 1000 mcg once daily orally is a possible alternative chronic regimen; avoid nitrous oxide |
| Neurolathyrism caused by neurotoxin beta-Noxalyl-L-alpha,beta-diaminopropionic acid | Diet largely consisting of grass pea (Lathyrus sativus), red chickling vetch (Lathyrus cicera) or purple Spanish vetchling (Lathyrus clymenum) | Spastic paraparesis typically developing over hours | MRI spinal cord, no specific findings | Diagnosis relies on history of exposure along with exclusion of other causes | Improved nutrition; avoid consumption of Lathyrus plants |
| Konzo caused by cyanogens | Diet largely consisting of bitter cassava (Manihot esculenta Crantz) | Spastic paraparesis typically developing over <1 week, with or without optic neuropathy | MRI spinal cord, no specific findings | Diagnosis relies on history of exposure along with exclusion of other causes; estimate cyanogen exposure by measuring urine or plasma thiocyanate | Improved nutrition, wetting method for cassava preparation, or avoid consumption of bitter cassava |
| Methotrexate (intrathecal) | Chemotherapy drug acting as folate antagonist | Subacute combined degeneration of the spinal cord, with or without peripheral neuropathy | T2 hyperintensity in posterior columns with inverted V sign; may extend over several levels in cervical or thoracic cord | Exposure to intrathecal methotrexate; low serum folate, high plasma homocysteine | Methotrexate cessation, folic acid supplementation |
| Tumor necrosis factor-alpha (TNF-alpha) inhibitors (eg, adalimumab, etanercept, infliximab) | Bind cytokine TNF to inhibit binding to TNF receptors, promoting neuroinflammation | Transverse myelitis | Variable, short-segment eccentric T2 hyperintensity or longitudinally extensive transverse myelitis, with or without gadolinium enhancement | Exposure to TNF-alpha inhibitor, with or without CSF oligoclonal banding | TNF-alpha inhibitor cessation, IV methylprednisolone 1000 mg once daily for 5 days, with or without plasma exchange |
| Immune checkpoint inhibitors (eg, ipilimumab, nivolumab) | Upregulate T cells by blocking anti-programmed cell death 1 (PD1)/programmed death ligand 1 (PD-L1) and anti-cytotoxic T-lymphocyte associated protein 4 (CTLA4) | Transverse myelitis | Variable, short-segment eccentric T2 hyperintensity or longitudinally extensive transverse myelitis, with or without gadolinium enhancement | Exposure to immune checkpoint inhibitor, with or without CSF oligoclonal banding | Immune checkpoint inhibitor cessation, IV methylprednisolone 1000 mg once daily for 5 days, with or without plasma exchange |
| Heroin | IV heroin administered after a period of abstinence | Acute onset of complete spinal cord syndrome, with flaccid paralysis, sensory level, and sphincter dysfunction | T2 hyperintensity involving the complete cross-section of the spinal cord, typically over several levels with predilection for thoracic cord | Exposure to IV heroin after period of abstinence | Avoid heroin, consider opiate reversal agent (eg, naloxone), IV methylprednisolone 1000 mg once daily for 5 days |
| Radiation | Fractionated or stereotactic radiation for malignancy | Delayed onset of myelopathy 6 to 24 months following radiation | T2 hyperintensity within prior radiation field, gadolinium enhancement | Prior exposure to radiation with exclusion of other causes | Dexamethasone, consideration of bevacizumab, avoid further radiation |
| Hepatic myelopathy due to accumulation of toxins, likely nitrogen products | Chronic liver disease with portosystemic shunting | Spastic paraparesis | MRI spinal cord no specific findings; MRI brain T1 hyperintensity in globus pallidus | Features in keeping with chronic liver disease | Liver transplant, shunt-limiting surgery |
| Decompression myelopathy likely due to nitrogen bubbles | Diving for prolonged duration with rapid ascent | Flaccid paralysis, sensory alteration, sphincter dysfunction within 1 hour of diving | MRI spinal cord; often no specific findings although T2 hyperintensity may be seen in posterior and lateral columns | Recent diving | Hyperbaric oxygen |
