Charles Bonnet syndrome in Leber’s hereditary optic neuropathy

Abstract

Charles Bonnet Syndrome (CBS) is a condition characterized by visual hallucinations in patients with visual loss and normal neuropsychiatric status. Although there is no consensus on diagnostic criteria for CBS, most experts describe stereotyped hallucinations, complex or simple, static or moving, with better clarity than expected given the residual vision [1]. The condition was first described by Swiss naturalist Charles Bonnet in his 87-year-old grandfather who had severe visual loss due to bilateral cataracts [2]. So far, only one patient with Leber’s Hereditary Optic Neuropathy (LHON) has been reported with CBS [3]. Here, we present ten patients (6 male, 4 female; age range 22–67 years) with genetically confirmed LHON who experienced CBS during the course of their disease. All patients suffered from acute-subacute onset of bilateral visual loss at age 15–65 years. The Table 1 summarizes their clinical characteristics, genotype and phenomenology of the hallucinations. Symptoms of CBS developed in a variable time after LHON onset, ranging from a few weeks to 10 years. In most of our cases, hallucinations occurred on a daily basis and lasted between few seconds to 1 h. Five of the patients had persistent hallucinations in the central visual field that only disappeared when falling asleep. While three patients developed complex hallucinations with vivid images of figures and animals, the others reported to perceive photopsias, various shapes or grid-like patterns. Hallucinations in Patient 4, 6 and 7 represented well-defined colourful geometric forms as is documented by one of the patient’s drawing (Fig. 1). None of the patients was aware of any triggering factor. Patient 1 presented at age 64 years with subacute bilateral visual loss. After genetic confirmation, treatment with idebenone 900 mg/day was started from 7 months after onset. 15 months after onset, she noticed simple visual hallucinations in the form of intermittent rosa-lila strips and some months afterwards, complex visual hallucinations, especially images of animals. The patient sometimes beats at the hallucinations, to get rid of the unpleasant perception, but she confirmed that she is always aware of their illusional nature. She had been reluctant to report her visual hallucinations, but showed significant relief when informed of their nature and how to deal with them. Patient 3 perceived images of monsters and stuffed toys as frightening and reported an improvement after receiving the correct diagnosis and an explanation of its benign nature. Hence, especially for patients suffering from complex visual hallucinations, a correct diagnosis of CBS and reassurance of the patient may lead to better outcomes. The visual hallucinations in CBS are thought to be caused by spontaneous discharges of the visual association cortex, occurring after deafferentation of visual inputs or damage to the visual pathway [1]. This may result in visual perceptions replacing the deprived stimuli, similar to auditory hallucinations in deafness or phantom pain syndrome. CBS with colour hallucinations has been primarily described in patients with age-related macular degeneration [4]. Functional MRI studies showed a hyperactive colour area of the visual association cortex resulting from damage to parvocellular pathways [4]. Selective involvement of papillomacular fibres belonging to the parvocellular pathway has also been observed in LHON, and is responsible for decreased contrast Hana Kolarova and Claudia B. Catarino contributed equally.