From this month, adults in Germany can legally possess and consume certain amounts of cannabis. While opinions on this development vary, it’s widely acknowledged that cannabis can pose potential health risks. Hajar Zebbakh and colleagues at the Ibn Sina University Hospital in Rabat, Morocco, have highlighted a potential complication of recreational cannabis use based on the case history of a young man.

The Patient and His Story 

According to the authors, the 24-year-old man was admitted to the clinic in Rabat experiencing status epilepticus. He reported a daily consumption of 8-10 cannabis joints since the age of 18 years, with no use of alcohol or tobacco.

The Findings

• Glasgow Coma Scale: 8 out of 15 
• Temperature: 36.8 °C 
• Stable cardiovascular status; SpO2: 91% 
• Leukocytosis: 25,000/mm≥ 
• Raised C-reactive protein and procalcitonin levels: 45 and 2.65 mg/L, respectively 
• Normal kidney function, and lactate and serum carboxyhaemoglobin levels 
• Electroencephalogram within normal limits 
• Cerebral computed tomography revealed no lesions 
• Cerebrospinal fluid analysis was normal 
• Toxicological blood test positive for cannabis, but negative for alcohol or other drugs 
• Cerebral MRI showed bilaterally symmetrical swelling of the hippocampi with high signal anomalies in T2-FLAIR and T2 sequences, hyperintense diffusion, and no enhancement after contrast injection 

Diagnosis: Acute hippocampal encephalopathy

Treatment and Course 

The patient received treatment that included intravenous acyclovir (10 mg/kg every 8 hours) despite negative PCR tests for herpes simplex viruses in the cerebrospinal fluid. Additionally, a corticosteroid bolus (500 mg/day), antibiotics, and immunoglobulins were administered due to suspected autoimmune encephalitis.

After initial intensive care, the patient was transferred to a general neurological ward. According to Zebbakh and her colleagues, the patient showed clinical improvement and was discharged from the clinic after 10 days.

Discussion

The authors explain that cannabis contains two psychoactive components, Δ9-tetrahydrocannabinol and cannabidiol, both of which target type 1 cannabinoid receptors found in the neural endings of several brain regions, including the hippocampus. This clarifies the involvement of the hippocampus in the case of the young patient. Additionally, these psychoactive components interact with type 2 receptors in immune cells.

Excessive cannabis use can lead to acute bilateral hippocampal lesions, as observed on FLAIR and diffusion sequences of MRI. In the case of the 24-year-old patient, other potential causes of bilateral hippocampal lesions, such as herpes encephalitis and autoimmune encephalitis, were ruled out.

A few years ago, French neurologists led by Laurent Cleret de Langavant from Assistance Publique-Hôpitaux de Paris, CHU Henri Mondor, France, highlighted the risk of acute hippocampal encephalopathy in heavy cannabis users in The American Journal of Medicine.

They reported similar findings in two men with heavy cannabis use (>10 joints/day), where MRI showed significant signal anomalies in the hippocampal regions. These patients also exhibited kidney dysfunction, rhabdomyolysis, and an inflammatory syndrome. However, no evidence of infectious or autoimmune encephalitis was found. Repeated electroencephalograms showed no epileptic activity. The acute clinical and magnetic resonance imaging findings improved within a few weeks. Notably, a subsequent exposure to cannabis led to a new encephalopathic episode. A few months later, both patients experienced severe and long-lasting impairments of episodic memory, along with hippocampal atrophy, as observed by the authors.

Cannabis is the most commonly used drug in Europe, according to Lars Wilhelm and Professor Jan Kramer and colleagues from LADR GmbH Medical Care Center in Geesthacht, Germany, as outlined in a journal article on the drug’s toxicology. Approximately 60% of the nearly 80 million consumers are male. Lifetime prevalence of cannabis use in Europe varies widely, ranging from 4% in Malta to 45% in France. Cannabis-related offences dominate drug-related crimes, with 57% of trafficking offences related to cannabis. The consumption patterns among today’s youth suggest a continued increase in the recreational use of cannabis as a narcotic drug.

In addition to the desired intoxicating effect of cannabis, undesirable effects also occur. These include impaired cognitive performance, particularly affecting memory, attention, and psychomotor skills. Regular use has been observed to lead to a drop of eight IQ points. However, cognitive restrictions are usually no longer detectable after prolonged abstinence. Furthermore, structural changes in brain regions with high CB1 receptor density, such as the amygdala and hippocampus, have been demonstrated, as reported by the two authors.