Nitrous oxide abuse
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Clinical radiological dissociation with subacute combined degeneration following Vitamin-B12 deficiency:case report A 24-year-old man developed subacute combined degeneration [SCD] secondary to vitamin B12 deficiency leading to clinical radiological dissociation following abuse of nitrous oxide. The man presented with numbness in all extremities and worsening lower-extremity weakness for about 20.days. He used to inhale about 100-200 cartridges of nitrous oxide on an average for at least 3 months for recreational purposes. He experienced mild weakness in the upper limbs (grade 4) and severe weakness in the lower limbs (grade 3). Neurological examination showed an increase in the vibration sensation, deep tendon reflexes, sensory ataxia and impaired joint position. Examination were consistent with positive bilateral Babinski, Romberg and Lhermitte’s signs. Laboratory tests revealed a decrease in levels of serum RBC, haemoglobin, vitamin B12 and folic acid. While homocysteine (Hcy) was noted to be elevated, this indicated functional vitamin B12 deficiency at the cellular level. MRI of the cervical spine demonstrated abnormal T2-weighted hyperintensity along the posterior columns extending from C2 to C6 on the sagittal image, with an additional inverted V-sign on the axial image. His diagnosis was confirmed to be SCD of the spinal cord induced by abuse of nitrous oxide. The man was treated with a high dose of supplementary intramuscular vitamin B12 injections and oral folic acid along with the cessation of nitrous oxide, which led to a gradual improvement in his symptoms. One month later, paraesthesia and weakness resolved. Although, he was able to walk unsupported, he showed residual gait impairment. The serum RBC, haemoglobin, vitamin B12, and folic acid levels were found to be normal. However, his serum Hcy remained elevated. Despite the improvement in his clinical symptoms and laboratory values, hyperintensities on T2-weighted images were identified, which extended, both horizontally and longitudinally, from C1 to T2. The hyperintensities resembled a ’ball’ on the axial images. He was discharged with a prescription for vitamin B12 supplements. His gait had improved, and he had only mild paraesthesia of the distal limbs at the 2-month follow-up. His serum Hcy normalised. The abnormal signals observed on T2-weighted images were noted to be decreased as compared to those noted at the 1-month follow-up MRI, although the images were more extensive than those seen in the prior MRI. The consistent lag between conventional MRI findings and clinical and laboratory manifestations suggested that a clinical radiological dissociation had occurred. Jiang J, et al. Clinical-radiological dissociation in a patient with nitrous oxide-induced subacute combined degeneration: a case report. BMC Neurology 20: 99, No. 1, 17 Mar 803499059 2020. Available from: URL: http://doi.org/10.1186/s12883-020-01685-5
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Reactions 5 Sep 2020 No. 1820
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