Neurotoxicity of nitrous oxide: multimodal evoked potentials in an abuser.
BACKGROUND
Nitrous oxide (N2O) damages the nervous system of chronic abusers. Multimodal evoked potentials (EPs) can help document the electrophysiological abnormalities of N2O abusers and its distribution in the nervous system.


METHODS
A 41-year-old male N2O abuser had used N2O (4-5 cans/per day, about 2000 ml/can) for more than 10 years. He complained of progressive motor clumsiness and distal paresthesia in the four limbs. Abnormal laboratory tests were megaloblastic red blood cells (102.3 fL, normal 80-94 fL) and serum vitamin B12 concentration of 143 pg/nL (normal 160-970 pg/nL). An MR image did not show significant findings in the brain but demonstrated conspicuous changes in the posterior and lateral columns at the C2-C7 level, in accordance with the anatomical lesions of the subacute combined degeneration of the spinal cord. In addition to sensori-motor axonal polyneuropathy, multimodal EPs showed abnormal visual EPs with prolonged peak latencies of P100, abnormal brainstem auditory EPs characterized by delayed wave V and difficulty in the recognition of waves I and III, abnormal somatosensory EPs with significant decreased peak amplitudes of cortical potentials bilaterally, and abnormal motor EPs to transcranial magnetic stimulation with prolonged central motor conduction time.


CONCLUSIONS
Our studies document electrophysiological abnormalities that may be attributed to N2O and indicate that N2O may indirectly involve multiple levels of the nervous system.
Lin
Chia-Yi
CY
Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan.
Guo
Wan-Yuo
WY
Chen
Shih-Pin
SP
Chen
Jen-Tse
JT
Kao
Ker-Pei
KP
Wu
Zin-An
ZA
Liao
Kwong-Kum
KK
D000328:Adult; D018685:Anesthetics, Inhalation / Q000009:adverse effects*; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009410:Nerve Degeneration / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D009609:Nitrous Oxide / Q000009:adverse effects*; D011115:Polyneuropathies / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology; D019966:Substance-Related Disorders / Q000209:etiology* / Q000473:pathology
D018685:Anesthetics, Inhalation; D009609:Nitrous Oxide