1519 - Subacute Combined Degeneration Secondary to Whip-it Inhalation: a case report

Subacute combined degeneration (SCD) secondary to nitrous oxide (NO) inhalation

Case Description:

35 year-old male presented to the hospital for a 3-week history of bilateral lower extremity weakness, paresthesia, and gait instability that began after month-long period of NO inhalation. He first noticed distal lower extremity paresthesia that spread proximally to his waist. This progressed to bilateral lower extremity leg weakness with associated gait instability resulting in falls. He also reported proximal spread of symptoms in his arms which had progressed to weakness, with urinary incontinence and saddle anesthesia. Exam revealed decreased muscle strength throughout and impaired sensation to vibration and light touch in lower extremities. He was found to have low B12 levels with macrocytosis. MRI showed abnormal T2 signals of dorsal cord at T4-T7. Electromyography noted evidence of an acute demyelinating process affecting motor nerves in bilateral lower extremities with early signs of demyelination in the upper extremities.

Discussions:

 B12 deficiency can cause various neurological pathologies, two of which are highlighted here. The first is a form of myelopathy known as SCD of the spinal cord, characterized by demyelination within the dorsal and lateral corticospinal tracts. Deficiency can also manifest with peripheral neuropathies, which can be an isolated finding or appear concomitantly with SCD as in this case.  Recreational use of NO  has been associated with B12 deficiency as NO can induce inactivation of B12 leading to diminished activity of enzymes essential for central nervous system myelination. Clinical findings of NO induced SCD consist primarily of a range of sensory and motor dysfunctions. Recent research shows a greater severity and more extensive symptoms in patients with NO induced SCD compared to SCD due to primary B12 deficiency.

Conclusions:

While SCD is most associated with B12 deficiency, recreational inhalation of NO can potentiate a more severe disease process in a younger population.