Marijuana-induced Transient Global Amnesia

A 6-year-old boy accidentally became intoxicated with marijuana secondary to ingesting cookies laced with marijuana. He presented with retentive memory deficit of sudden onset that was later diagnosed as transient global amnesia. Transient global amnesia as a result of marijuana intoxication is an extremely rare event.

Transient global amnesia is typically described as amnesia of sudden onset regarding events of the present and the recent past. It can be associated with retrograde amnesia and typically occurs without any focal neurologic deficit. ^1-3 This neurologic disorder is usually encountered in elderly people. We present a case of transient global amnesia from acute marijuana intoxication in a 6-year-old boy. To our knowledge, transient global amnesia as a result of marijuana intoxication has not been reported previously in such a young child.

Case Report

Paramedics brought a 6-year-old boy to the emergency department (ED) because of his strange behavior of sudden onset. Paramedics stated that they were called to the school, where a teacher reported that this first-grader started to display behavior that was inconsistent with his usual personality. When she noticed that although the little boy had done his math quizzes correctly, he kept on saying, I don't know what am I doing here, she called 911 for help. On arrival at the ED, the boy repeatedly said, How did I get here? Later on, when his parents arrived at the ED, they did not report anything unusual occurring before the child left home for school. His medical history was unremarkable.

Key Points

* A 6-year-old boy was accidentally exposed to marijuana.

* The patient presented with retentive memory deficit of sudden onset, which is typical of transient global amnesia.

* Transient global amnesia from marijuana intoxication is an extremely rare event.

The physical examination revealed vital signs as follows: temperature, 36.1°C (97°F); heart rate, 135 beats/min; respiratory rate, 24 breaths/min; and blood pressure, 100/65 mm Hg. The patient was alert but appeared to be anxious. There were no external signs of physical injury. Head, ears, eyes, nose, and throat; neck; lungs; and abdomen were normal on examination. Cardiac examination was unremarkable except for tachycardia. On neurologic examination, he was alert and aware of the surroundings. His speech was normal. He had retentive memory impairment and did not demonstrate any retrograde amnesia. Both pupils were 5 mm, equal, round, and reactive to light. He did not have any nystagmus. He had fine tremors in the upper and lower extremities. Deep tendon reflexes were 3+in all four extremities, and his gait was ataxic.

Pulse oximetry showed oxygen saturation of 96% on room air. A bedside Dextrostix revealed glucose of 96. An IV line was established. Cardiac monitoring showed sinus tachycardia with a heart rate of 135 beats/min. His complete blood count, sequential multiple analysis (seven different serum tests), liver enzymes, urinalysis, electrocardiogram, and computed tomographic scan of the brain were unremarkable. The patient required a total of 4 mg of lorazepam IV in the ED for agitation. Since he still had altered mental function, a lumbar puncture was performed, and cerebrospinal fluid laboratory values were also unremarkable. Urine toxicologic screen came back later, and it was positive for cannabinoids. Per toxicologic consultation, he was observed in the ED for 4 hours, but his mental status did not improve.

Due to altered mental status and ataxic gait, the patient was hospitalized. His tachycardia resolved, and his blood pressure returned to normal. A neurology consultation was obtained. He was diagnosed as having transient global amnesia secondary to marijuana intoxication. The boy's memory returned to normal after a period of 14 hours.

Psychiatry, social services, and Child Protective Services (CPS) consultations were also obtained. On the third day of his hospital stay, during psychiatric interrogation, his mother admitted to having baked marijuana cookies, which she had left out on the kitchen table. She also said that the boy must have eaten those marijuana cookies. The CPS transferred the boy to a foster care home while the parents underwent legal proceedings for child neglect and possession and use of marijuana. The patient's neuropsychiatric follow-up visits at 6 months and subsequently at 12 months were satisfactory, except that he had no recall of the entire episode.

Discussion

Our thorough search of the medical literature using the National Library of Medicine's MEDLINE database failed to reveal a single case of transient global amnesia (TGA) from acute marijuana intoxication in a young child. Lack of history of illicit drug use can pose a diagnostic challenge in the management of patients with altered mental status. Once the organic and metabolic causes of altered mental status such as intracranial hemorrhage, mass, hypoglycemia, sepsis, and thyrotoxicosis have been ruled out, intoxication from alcohol and drugs should be considered. Cocaine or amphetamine intoxication may present similar to marijuana intoxication, except that the patient may show more signs of aggression with the former. Opiates should be suspected when the patients present with pinpoint pupils. Phencyclidine should be suspected if the patient presents with extremely combative behavior. Marijuana intoxication should be suspected when a patient presents with unexplained impairment of cognitive functions.

The classic presentation of transient global amnesia includes pronounced memory loss for recent events in the absence of focal neurologic signs. It is remarkable that consciousness is well preserved in these patients. ¹ The annual incidence of TGA has been estimated as 5.2 per 100,000 population. ⁴ It is typically encountered in the middle-age or elderly population, and is considered to be a very rare occurrence in children. ⁵ In this condition, the patient presents with characteristics of retrograde amnesia that lasts for less than 24 hours. ⁶ The patient may have difficulty in forming new memory, as illustrated by our case. Amnesia gradually resolves over several hours as the patient recovers.

Development of TGA has been reported with migraine, arterial embolism, polycythemia, tumor of the temporal lobe, exposure to cold-water immersion, acute painful events, alcohol, medications (eg, digoxin, chloroquine, benzodiazepine, diclofenac), severe emotions, and, rarely, marijuana. ^1,7 It is likely that TGA from marijuana may occur as a result of one of two possible mechanisms. In the first possible mechanism, vasospasm, it has been suggested that TGA is caused by transient ischemia of the hippocampal region, probably as a result of vasospasm of the vertebrobasilar arterial system. ⁸ The second mechanism of interference postulates that transient global amnesia results from the action of cannabinoids at receptors located in the intermediate pyramidal cell layers of the hippocampus, the dentate gyrus, and layers I and VI of the cortex, where memory is stored. ⁹

When consumed in high doses, marijuana affects the cognitive functions of the brain. The patient may present with incoherent conversation; difficulty with speech fluency; inability to perform complex tasks; and acute panic state, anxiety, euphoria, delusions, agitation, drowsiness, nausea, and impaired motor function. Patients can also develop illusions and bizarre behavior.

The diagnosis of transient global amnesia from marijuana use can be difficult to make in the ED when the history is unavailable or when polydrug ingestion is involved, thus placing emphasis on the initial drug-screening test. In our case, the TGA was very likely caused by marijuana. It was the only agent of importance in the cookies that were eaten by the child, and his urine toxicologic screen was found to be positive for cannabinoids.

TGA is known to resolve spontaneously, and therefore it may not require any intervention. In general, one must start with stabilizing airways, breathing, and circulation. Mild agitation may require reassurance only. For children with acute agitation, benzodiazepines such as diazepam 0.2 mg/kg administered IV or lorazepam 0.05 to 0.10 mg/kg administered IV are the drugs of choice. If a second sedating agent is needed, haloperidol 0.05 to 0.15 mg/kg/24 hours can be administered orally and repeated every 8 to 12 hours as needed. Gastric emptying and administration of activated charcoal should be considered for ingestion that has occurred within 1 hour of presentation, large ingestion, or when other co-ingestants are suspected. Hemodialysis is not helpful for marijuana ingestion.

Once a child with mild clinical features has been observed for approximately 4 to 6 hours in the ED and has done well, they can be safely discharged and sent home with their parents. If acute psychosis does not abate, psychiatric evaluation and admission are warranted. The presence of medical complications also warrants hospitalization. Whenever child neglect is suspected, CPS and social services must be consulted.

Conclusion

Since marijuana use is currently prevalent in society, children can sometimes be exposed to marijuana inadvertently and develop serious complications. Transient global amnesia due to marijuana intoxication, as in our case, illustrates such an unfortunate event.