Rapidly Progressive Dementia and Myoclonus

SIR: Dementia with Lewy bodies (DLB) is a lately identified concept based on a clinical and pathological correlation: progressive disabling mental impairment with peculiar features such as hallucinations, fluctuating cognition or motor parkinsonism, and cortical with or without subcortical Lewy bodies.¹ We report briefly two cases with unusual features of DLB.

Case Reports

Case 1. A 74-year-old woman with no significant medical history but with depression 1 year ago began complaining of slowness of movements. Examination disclosed mild features of parkinsonism, including reduced armswing, rigidity, and bradykinesia, without resting tremor. Mini-Mental State Examination (MMSE) score was 30/30. Shortly after low doses of levodopa (150 mg) were given, parkinsonian features receded, but visual complex hallucinations arose. These hallucinations were not recognized as unreal and even worsened after levodopa was stopped or clozapine was given. Cognitive impairment appeared 7 months later. Hospitalization then occurred as myoclonus became evident. MMSE was 6/30, with perseveration and rigid-akinetic signs at examination. Decline was markedly rapid, and the patient died 8 months after the onset of the symptoms. Brain computed tomography (CT) revealed cerebral atrophy. EEG showed triphasic complexes without periodicity. 14-3-3 protein was not detected in the cerebrospinal fluid (CSF). Diffuse cortical Lewy bodies were found at autopsy.

Case 2. A 72-year-old man with history of tobacco addiction and asbestosis presented with a 1-year history of progressive forgetfulness. Examination disclosed mild temporospatial confusion, dressing and ideomotor apraxia, and bilateral cogwheel rigidity. Language and attention were well preserved. Brain CT was normal. Six months later, the patient came to the hospital for cognitive impairment with shuffling gait. Examination showed akinesia and rigidity. MMSE was 9/30. Routine biological investigations were unrevealing, with no changes on brain CT. EEG showed slow left activities. Four months later, the patient was admitted to the hospital bedridden in the course of continuous and progressive decline. He was alert but unresponsive to voice. Examination disclosed rest myoclonus increased by noise, with no pyramidal features or focal signs. There was biological evidence of dehydration, with elevated natremia and creatinemia. CSF was germ-free, without pleocytosis. EEG showed slow delta activity without periodic discharges. The patient died 5 days after admission. Autopsy disclosed numerous senile plaques, neurofibrillary tangles, and cortical and subcortical Lewy bodies without spongiform changes.

Comment

Both of these case reports are of particular interest because the patients evolved very rapidly to a fatal outcome (8 and 22 months) and had myoclonus in the late stage. Mean duration of DLB ranges from 5 to 8 years,² although a 22-month duration has been described.³ Myoclonus is uncommon in DLB and was not mentioned in the first clinical descriptions.^4,5 Although not excluded, it is not a feature essential to or supportive of the diagnosis of DLB.¹ Myoclonus in patients with a rapidly progressive form of dementia raises the suspicion of Creutzfeldt-Jacob disease. Once a prion disease is ruled out, DLB should be considered in such patients.