usually, more cord expansion often enhance ependymoma: not particularly of dorsal columns.astrocytoma: not particularly of dorsal columns.HIV vacuolar myelopathy: may appear very similar.transverse myelitis: although longer in length, usually not restricted to dorsal columns.multiple sclerosis: also affects dorsal columns but usually over a shorter length.

vitamin E deficiency: can look identical.

copper deficiency myeloneuropathy: can look identical.

other etiologies of subacute combined degeneration of the cord.

On imaging, the differential diagnosis includes: By 1844, Horace Wells, an American dentist, had reported its usefulness as an anesthetic gas. Within only a few years it was already being abused as a recreational 'high', aware of this Humphrey Davy coined the term 'laughing gas' 7,8. Nitrous oxide gas was first synthesized in 1772 by an English theologian and chemist, Joseph Priestly, chiefly remembered historically for his discovery of oxygen.

methionine supplementation has also been used 2ĭespite optimal treatment, some patients are left with a permanent deficit, including lifelong paraparesis.Īlthough there is no risk of physical addiction, the risk of a psychological N 2O habit is a clear and present danger 8.

high dose of intramuscular vitamin B 12, followed by oral supplementation.

T2: thoracic hyperintense signal involving the dorsal columns ( inverted 'V' sign), although less commonly lateral tracts of the spinal cord may also be affected very rarely is there involvement of the anterior spinal cord.

Radiographic features are identical to those of subacute combined degeneration of the cord. The end result of overexposure is demyelination and eventual gliosis, both within the central nervous system and to a lesser extent the peripheral nervous system.

Neurotoxicity is secondary to the selective inhibition of vitamin B 12 (hydroxocobalamin), which serves as a cofactor for methionine synthase, which is an enzyme active in folate metabolism and the formation of myelin sheath phospholipids 2,4. The classic neurological appearance of vitamin B 12 deficiency is the so-called subacute combined degeneration of the cord manifested as damage to the dorsal columns of the spinal cord, responsible for the transmission of vibratory and proprioceptive input. Peripheral neuropathy, optic atrophy, and dementia can also occur. Pre-existing vitamin B 12 deficiency increases the risk of nitrous oxide-induced toxicity 8. In the 2013/14 Crime Survey for England and Wales, it was reported that almost 8% of 16 to 24-year-olds had used nitrous oxide recreationally in the previous 12 months 8. Physiologically, its effects manifest within seconds of inspiring the gas, and its offset is just as rapid, with no after effects, such that users may continue with their regular activities only minutes post-exposure. As an end-user, nitrous oxide gas is a close-to-ideal recreational agent, it is legal, inexpensive, easily accessible, and not found on standard illicit substance screens.

Gas inhale mr contrast