Abstract

An 18 year old man was admitted following a suspected seizure after inhalation of the legal high ‘Sirius’. The following day he was still suffering from mild disorientation and impaired short term memory (scoring 20/30 on Montreal Cognitive Assesment). An MRI brain revealed marked bilateral medial temporal lobe high signal which enhanced following contrast. Blood tests were normal and he gradually improved to his normal self over the three days following admission. A repeat MRI is pending to investigate whether the imaging changes have resolved.

Sirius is a synthetic cannabinoid receptor agonist that mimics the effects of cannabis. It is available on the internet or in head shops where it is sold as herbal incense.

Legal highs (or ‘Novel Psychoactive Substances’) are recreational drugs not covered by current misuse of drugs laws, so are legal to possess or use. With the increase in number, availability, and consumption of these products neurologists need to be aware of the potentially serious neurological risks associated with their use. The novel MRI findings reported in this case suggest that they should also be considered in the differential diagnosis of patients presenting with suspected viral and immune-mediated encephalitides.