Neurology Case Challenge: Visual and Auditory Hallucinations in a Patient With Parkinson Disease

Lee Neilson, MD; Elena Cecilia Rosca, MD, PhD; Simu Mihaela, MD, PhD; Chirileanu Ruxanda Dana, MD, PhD

Disclosures

January 24, 2022

The main differential diagnostic consideration in DLB is Parkinson disease dementia (PDD) because the clinical features of DLB are very similar to those of PDD. They share many pathologic and clinical features, probably representing 2 clinical entities on a spectrum of Lewy body disease.[13] Although no clinical or pathologic basis can determine a definite time interval between the development of motor symptoms and the onset of dementia in differentiating DLB from PDD, to avoid confusion in clinical practice, a diagnosis of DLB should be made when dementia precedes or occurs within 1 year of the development of motor symptoms, whereas a diagnosis of PDD is appropriate when dementia develops within the context of established Parkinson disease.[9,14]

In this case, cognitive features appeared 7 months after extrapyramidal symptoms. Furthermore, the motor signs did not respond well to levodopa. Given these facts and the features described above, DLB was suspected.

Other entities in the differential diagnosis for this case include vascular dementia and AD. This patient had lacunar infarcts, which can cause vascular parkinsonism and dementia, but the neuroimaging results showed that the cerebrovascular disease was not of sufficient severity to account for all of his cognitive deficits. DLB can occasionally be confused with AD. In fact, half of all individuals with DLB are estimated to have sufficient pathology for a secondary neuropathological diagnosis of AD at autopsy.[15] However, patients with DLB more frequently have frontal lobe dysfunction, with marked impairment on tests of executive function and attention. In addition, those with DLB perform significantly worse on visuospatial tests than those with Parkinson disease, and their visual hallucinations are more prominent. Patients with AD also have poorer memory task performance. This disproportionate performance in different cognitive domains may help differentiate DLB from AD.[16] This patient's pattern of cognitive impairment, visual hallucinations, and fluctuating cognition favors a diagnosis of DLB.

Other potentially reversible or treatable causes of dementia must also be excluded. American Academy of Neurology (AAN) guidelines recommend screening for B12 deficiency, hypothyroidism, and depression. The normal vitamin B12 and folate levels ruled out these nutritional deficiencies. The normal thyroid panel excluded hypothyroidism as a cause for the patient's presentation. Testing for syphilis and HIV is typically reserved for situations with a high clinical suspicion, based on sexual history or travel to areas where exposure is more common. In this case, the patient’s results were negative.

The cerebral CT scan was performed to assess for structural pathology, such as a subdural hematoma (which can cause fluctuating cognition), a mass lesion (which can cause various symptoms and signs), or signs of normal pressure hydrocephalus (which presents as gait disturbance sometimes reminiscent of parkinsonian gait, dementia, and urinary incontinence and may require an MRI scan with a cerebrospinal fluid flow study for further imaging confirmation). Other indicators that warrant additional workup may include rapid decline in function, younger age of onset, prominent fluctuations, high-risk exposures, high-risk behaviors, unexplained neurological examination findings, and incongruent performance on neuropsychological testing.[17]

This patient's carbidopa/levodopa was stopped because this treatment can exacerbate behavioral or psychotic symptoms and because the patient had no demonstrable improvement. Only modest evidence is available for the treatment of DLB symptoms; however, expert consensus does offer some management strategies.[18] Data on the best treatment option for motor symptoms in patients with DLB are insufficient. Levodopa can improve motor function and is least likely to aggravate psychosis, but its risk-benefit ratio must be considered. The use of other Parkinson disease medications, such as anticholinergics, catechol-O-methyl-transferase inhibitors, monoamine oxidase inhibitors, and amantadine, may exacerbate cognitive impairments and should be avoided.[19] Zonisamide, a common antiseizure medication, has been shown to improve motor function without exacerbating psychiatric symptoms at doses of 25-50 mg/day when given as an adjunct to levodopa.[20]

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