Gerald Burgess, a University of Leicester lecturer in clinical psychology, has described treating an individual who suffered a “Memento/Before I Go to Sleep“-style anterograde amnesia memory loss after a treatment at a dentist — “like nothing we have ever seen before.”

Since the one-hour root-canal treatment, during which the a 38-year-old man from the UK was given a local anesthetic, the individual cannot remember anything beyond 90 minutes.

He is fully aware of his identity and his personality did not change, says Burgess, but every day the man thinks it is the day of his dental appointment. He has to manage his life through an electronic diary and access to prompts.

Burgess has now described the study, done a decade ago, in an open-access paper published in May in the journal Neurocase. He is also appealing for people who know of someone who might have suffered similar symptoms of memory loss, or medical or allied health professionals working with someone like this, to contact him to build up knowledge and evidence in this field of study.

Possible explanations

Burgess notes that “what we did know about from decades of research and hundreds of case studies, is that bilateral damage to the hippocampal and/or diencephalon structures causes profound amnesia … [but] we should perhaps not be so stuck in thinking that profound amnesia only occurs in the context of visible damage to the brain’s hippocampal and/or diencephalon structures.

“Those structures appear just to be needed for the initial holding or retention of information before engrams then proceed slowly through several other neuro-electrical and neuro-chemical events, before finally permanent memories are stored, and that something can occur at some later point in this process to vanquish the memory trace permanently.

“An acquired or manifest deficiency of protein synthesis, required for permanent re-structuring of synapses in the brain, seemed an intriguing speculation, and one we hope there might be further human research into. This speculation was sparked by two seemingly key coincidences of one, timing when this protein synthesis stage occurs coincides with the patient’s forgetting at 90 minutes or thereabouts, and two, both ‘episodic’ and ‘procedural’ memories appear to require successful protein synthesis to occur for long-term memory permanence, and the patient cannot retain any new either episodic or procedural memories — and this is unusual compared to traditional cases of amnesia.”

The work was done in collaboration with Bhanu Chadalavada Consultant Psychiatrist at Northamptonshire Healthcare Foundation NHS Trust.

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Abstract of Profound anterograde amnesia following routine anesthetic and dental procedure: a new classification of amnesia characterized by intermediate-to-late-stage consolidation failure?

Anterograde amnesia caused by bilateral hippocampal or diencephalon damage manifests in characteristic symptoms of preserved intellect and implicit learning, and short span of awareness with complete and rapid forgetting of episodic material. A new case, WO, 38-year-old male with anterograde amnesia, in the absence of structural brain changes or psychological explanation is presented, along with four comparison cases from the extant literature that share commonalities between them including preserved intellect, span of awareness greater than working memory, and complete forgetting within hours or days following successful learning, including notably for both explicit and implicit material. WO’s amnesia onset coincided with anesthetic injection and root canal procedure, with extended vasovagal-like incident. The commonalities between the five cases presented may suggest a shared biological mechanism involving the breakdown of intermediate-to-late-stage consolidation that does not depend on the structural integrity of the hippocampi. Speculation on the mechanism of consolidation breakdown and diagnostic implications are discussed.