Chronic Lithium Neurotoxicity Presenting as Dementia: A Case Report

Introduction Treatment with Lithium can be associated with a continuum of neurological side effects, ranging from benign tremors to early reversible lithium neurotoxicity, to chronic irreversible lithium neurotoxicity. Among chronic systemic adverse effects of Lithium, neurotoxicity has been reported to be the most common, followed by renal and cardiovascular toxicity (Sunn et al). Data on lithium toxicity in the elderly is limited but available data indicates that adverse effects occur more commonly in the context of chronic therapeutic administration of lithium rather than instances of overdose (Oakly et al). EEG and nerve conduction studies show notable changes that correlate with the increased duration of Li therapy (Fountoulakis et al). Older adults are more susceptible to side effects even with “normal” lithium levels for reasons such as declined renal function, reduced volume of distribution, medical comorbidities, concomitant medications, and drug interactions. Here we present a case of an elderly man with chronic lithium neurotoxicity associated with significant cognitive changes and severe disability. This will be followed by a review of literature of chronic lithium neurotoxicity in the geriatric population. Methods Case of Mr. A: We present the case of a 72 year old man who presented to the Memory Clinic with a diagnosis of Alzheimer's disease (AD) since the age of 55. His presentation was also notable for progressive aphasia and he had a PEG tube placed for feeding. His cognitive deficits were most significant in the domains of executive and visuospatial functioning, memory, and language. Physical exam findings were notable for mild left hand tremor, difficulties with balance, slow gait with short steps and a decreased arm swing, limited vertical gaze, and dysphagia. He was independent with his ADLs but dependent on IADLs due to aforementioned cognitive and physical findings. Other psychiatric diagnoses included Bipolar Disorder, Substance Use Disorder in remission. At the time of his evaluation, Mr. A had been on Lithium for over 20 years with records for the past three years showing therapeutic levels .5-1.1mmol/L. Although the patient had been previously diagnosed with AD, his relatively stable neuropsychological profile over the last 15 years called the diagnosis of AD into question and this was confirmed by negative amyloid imaging. The patient had yearly therapeutic levels of Lithium until his wife's concern for further insidious cognitive decline in the domains of language and memory, along with worsening gait and tremor prompted checking a Lithium level which was 1.8. Patient was subsequently weaned off Lithium over several months. At the time of this writing this abstract, Mr. A's cognition and motor function are significantly improving, to the extent of no longer requiring PEG for dysphagia. Electronic searches of The Cochrane Central Register of Controlled Trials and the standard bibliographic databases PubMed, MEDLINE, EMBASE, and PsycINFO will be performed for papers focusing on chronic lithium neurotoxicity in older adults. Keywords include “lithium” and “adverse effects” or neurotoxicity” or “neurological manifestations.” Original research, case reports, and reviews will be included. Data focusing on older adults will be extracted and presented. Results Initial search for literature focusing on chronic lithium neurotoxicity yielded 4 papers. Data from these papers will be extracted. The range of neurological adverse effects, both physical and mental, will be described. This will be followed by a discussion of risk and precipitating factors for lithium neurotoxicity. Association with lithium doses, duration of treatment, and serum lithium levels will be elucidated. Lastly, diagnosis and treatment considerations will be highlighted. Conclusions Chronic lithium Neurotoxicity is more common in the elderly and can occur at normal to even sub therapeutic doses. It is imperative to have an optimal index of suspicion if an individual on chronic lithium therapy presents with cognitive deficits. Funding not applicable