Case report
An 85 years old man presented with a first episode of sustained complex visual hallucinations that started suddenly three days earlier. He saw “ancient Greek statues” and the number six in the center of his visual field. The hallucinations appeared each morning right after eye opening and lasted all day. The patient was perfectly aware of the imaginary nature of the images but found them very disturbing. He could make them briefly disappear by closing his eyes but the same images reappeared some seconds after eye reopening. He had a history of multi-infarct syndrome, severe bilateral visual loss due to vitreous hemorrhages, and Parkinson's disease (PD) that had been diagnosed three years earlier and responded well to levodopa (3 × 250 mg). His treatment consisted otherwise of warfarin and antihypertensive drugs and had not been changed in the last three years.
Neurological examination revealed mild hypophonia and hypertonia of both arms as the sole motor manifestations of PD. Even at very close distance, the patient was unable to read a text with a 36 font size. He had no dementia but presented with mild cognitive impairment of the dysexecutive type at formal neuropsychological testing, with a Mini-Mental Status Exam of 27/30 that was stable since PD diagnosis.
Suspecting a Charles Bonnet syndrome (CBS), treatment with carbamazepine (2 × 100 mg) was started. Three days after treatment initiation, the hallucinations had disappeared completely. One month later, the treatment was discontinued because the patient complained of gait instability. This instability resolved after treatment withdrawal, without the reappearance of hallucinations.
Discussion
In this patient, the combined presence of full insight, severe bilateral vision loss, and clearly formed recurrent and persistent unimodal visual hallucinations suggested the diagnosis of CBS. The immediate appearance of the images at eye opening in the morning and their long duration suggested that the hallucinations were not due to PD or its treatment, as Parkinson-related hallucinations occur more often at the end of the day, tend to be episodic, and much shorter in duration (Manford and Andermann, Reference Manford and Andermann1998; Bertram and Williams, Reference Bertram and Williams2012).
CBS is thought to be a cortical release phenomenon and should only be pharmacologically treated when it is disturbing for the patient and when the underlying cause of the vision loss cannot be treated (Kester, Reference Kester2009). Despite its non-epileptic etiology, several case reports have shown that low-dose antiepileptic treatments like carbamapezin, valproic acid, or gabapentin can lead to a full symptomatic relief (Unni et al., Reference Unni, Venugopal, Gupta, Rani and Patro1996, Holroyd and Sabeen, Reference Holroyd and Sabeen2008; Segers Reference Segers2009).
Despite the high frequency of both pathologies, the comorbidity of CBS and PD is uncommon (Alcántara et al., Reference Alcántara, Valenciano, Díaz-Ortuño, Martinez-Navarro and Barcia1998) but underdiagnosis of CBS in PD patients is likely the result of underdiagnosis of CBS in general (Schadlu et al., Reference Schadlu, Schadlu and Shepherd2009). This case report shows that it can be easily treated without the need for reducing dopaminergic treatment or the initiation of potentially harmful neuroleptics. Physicians treating PD patients should be familiar with CBS and consider it as a potential alternative etiology for visual hallucinations, especially when the patient has severely impaired vision and when the hallucinations are sustained during wakefulness.
Conflict of interest
None.
