Although there have been a limited number of case reports of human bilateral hippocampal injury, none of these have addressed the impact of such injuries on medical decision making capacity. The authors present a case of an elderly man with discrete bilateral hippocampal injury. As a result of his injury, the patient was hopelessly “lost in the present” and only retained the basic cognitive functions necessary to have decision making capacity for a limited period of time. He was unable to appreciate the nature of his injury, the potential risks involved in his decisions, and the recommended course of treatment longer than a few minutes. The patient’s resultant neu rocognitive deficits left him lacking medical decision making capacity, a likely outcome for patients with persis tent anterograde amnesia.
Numerous studies and cases have explicated the role of the hippocampus and structures of the medial temporal lobe in memory, learning, and behavior. Scoville and Milner [
As with other structural insults, bilateral hippocampal damage may present with a range of deficits, not solely dense amnesia. Often, autobiographic memory and semantic memory are preserved [
Consult-liaison “CL” behavioral health teams are often asked to determine a patient’s capacity to make medical decisions. One study placed these assessments at 25% of all referrals to such teams [
There have been limited case reports of human bilateral hippocampal injury and no reports regarding the impact of such injuries on medical decision making capacity (DMC). Bolouri and Small [
“LN”, a 70-year-old unmarried male, was brought to the emergency room after a two-day absence from work. LN was confused, oriented only to person and place. He had facial abrasions and contusions but could not recall a fall or other recent trauma. In fact, he lacked any recollection of the preceding week. LN’s initial medical workup was unremarkable. He denied significant medical history and related that he had not seen a doctor in over 20 years. Though he acknowledged moderate alcohol use, LN repudiated clinicians’ suspicion of recent illicit substance use. However, a subsequent urine toxicology screen was found positive for cocaine. Because of his continued altered mental status and obvious memory disturbance, LN was admitted to the inpatient medical service. There, consulting neurologists confirmed his persistent anterograde amnesia and recent retrograde amnesia, but found neurological functioning otherwise grossly intact. Though serial CT studies revealed no acute intracranial abnormalities, a subsequent MRI revealed restricted diffusion in the bilateral hippocampi consistent with ischemic infarctions. It is believed that LN’s cocaine use caused this markedly discrete neurological damage, possibly secondary to seizure activity and associated hypoxia. In adults, the hippocampus is particularly vulnerable to cerebral ischemia [
On hospital day four, the CL service was consulted for an opinion on LN’s capacity to make medical decisions. Unable to understand why he was being kept in the hospital, LN had become increasingly agitated and was demanding to leave against medical advice. An occupational therapy evaluation from the prior day expressed an opinion the patient was unsafe to return home alone noting his inability to find his room after a brief walk. LN was cooperative but guarded with the CL team during the initial assessment. Although oriented to person and place, LN could not identify the date or day of the week. He complained that his physicians had not explained the cause of his difficulties. LN appeared genuinely perplexed when the CL team reviewed chart notes detailing no less than six conversations with his primary team about his situation. The CL team noted LN’s concrete and perseverative thought process. He lacked awarenessof the cause or extent of his cognitive deficits. The team found LN lacking medical decision making capacity to leave against medical advice and agreed to follow him to monitor his mental status and behavior.
Two follow-up assessments were completed on hospital day six and seven. On the occasion of the first follow-up, LN refused to cooperate with the examination. He angrily demanded, “We need to get down to business on why I’m being kept here like a criminal!” Though conceding “memory difficulties,” he minimized his dysfunction. Members of his primary team, whom LN could not recall between visits, noted his repeated demands to speak to “my doctor”. On each successive explanation of his injuries and associated deficits, LN experienced dysphoria and agitation.
On the following day, two other CL team members met with LN to test for any improvement in his mental status. LN’s affect brightened immediately on the team’s introduction and he expressed his gratitude that “somebody has finally come to help me!” When again asked the reason for his admission, LN thought for a while then stated that he didn’t know for sure but that it might have something to do with his “short term memory”. He then offered that he had fallen and struck his head and deduced that “must have been” the precipitating event. On direct questioning, LN admitted he had used cocaine and alcohol in the recent past. The team wondered if this represented some temporal recovery in his retrograde memory loss.
LN was attentive to the CL team’s explanation of neuroanatomy and the locus of his injuries. He asked reasoned, appropriate questions during the discussion. However, as the interview progressed, LN demonstrated a stark inability to remember the content of conversation after an interval of only several minutes. On at least ten occasions over the course of an hour, LN inquired, “Doctor, can you tell me what’s wrong with me?” He responded well to, and was comforted by, therapeutic interventions targeted at his feelings of loss and terror caused by his memory disturbance. Reaffirming LN’s lack of decision making capacity for medical decisions, the CL team met with his physicians to suggest behavioral and orientation strategies.
LN’s case illustrates the profound importance of hippocampal functioning and learning for retention of DMC. LN was able to voice his preference—sometimes quite forcefully—to leave the hospital. However, the simple ability to articulate a preference does not necessarily correlate with a patients’ ability to reason or act in his selfinterest. In its Study of Ethical Problems in Medicine and Biomedical and Behavioral Research the President’s Commission rejected the solitary “expressed preference” standard [
In service of self-determination, a patient needs a stable set of values against which to weigh treatment outcomes [
In a recent study of 60 patients suffering amnestic mild cognitive impairment, Okonwo et al. [
As described above, LN was attentive to explanations of the specific brain insults apparent on imaging. He apprehended the expected consequences of hippocampal damage on memory consolidation. Moreover, LN asked insightful and reasoned questions about the persistence and specificity of his memory deficits. However, his ability to understand information in the moment did not translate into knowledge. Unable to consolidate information into declarative memory, LN could not learn. When asked gently what was just explained to him, LN replied, “I don’t know; am I missing something?” More specific questions, such as “do you remember me explaining the hippocampus?” evoked apparent frustration, confusion, embarrassment and disbelief.
LN developed little appreciation for his persisting injury. His only complaint, which he reported matter-offactly, was the sense that his “short term memory” was troubled. Unable to recall explanations of his illness, LN was caught in an unrelenting state of not knowing what he didn’t know. Because of preserved processing capacities, LN’s anosognosia was qualitatively different from that often seen in patients with Alzheimer’s dementia. When made evident to him, LN was both appreciative of and frightened by his deficits.
So important is memory to DMC, the U.K. legislature [
Future orientation is another important capability supporting DMC. Memory impairments may dramatically compromise future orientation. A patient who retains capacity is able to provide a rationale for his or her expressed, consistent medical decision that considers the facts of the condition/impairment, the alternatives available, and explain how that choice reflects goals and values [
Amnesic patients may be unable to imagine new experiences troubling future orientation. In a small sample study, Hassabis, Kumaran, Vann and Maguire [
LN’s deficits in future orientation were evident on examination. A custodian, LN’s job required him to travel to multiple sites. Asked how he would be able to compensate for his ongoing memory deficits to perform his job, LN protested, “I don’t know; I guess I’ll just remember.” Consistent with the constructive episodic simulation hypothesis [
In evaluating DMC, clinicians must balance patient autonomy and self-determination with patient well-being. The consequence to the patient for a given decision informs the level of impairment necessary to obviate his capacity [
Gutbrod et al. [
Patients with persistent anterograde amnesia have a unique constellation of neurocognitive deficits leaving them unlikely to retain DMC. Compromised declarative and episodic memory confounds their ability to manipulate relevant information on condition, prognosis, and treatment alternatives. Although their historical values structure may be preserved, disrupted learning may prevent informed, value-consistent choices. Patients with bilateral hippocampal damage are likely to demonstrate marked impairment in future orientation. Unable to retain information on the extent of their dysfunction, imagine future events, and understand the viewpoints and motivations of others, these patients are extremely vulnerable to manipulation and exploitation.