Coexistence of Charles Bonnet Syndrome and occipital epilepsy: A diagnostic challenge

Highlights

• •Comorbid Charles Bonnet Syndrome and occipital epilepsy is rare occurrence.
• •This comorbidity poses a great diagnostic challenge.
• •EEG capturing the clinical events can aid in the diagnosis.
• •Understanding the phenomenon is crucial for diagnosis and effective management.

Abstract

Charles Bonnet Syndrome (CBS) is a condition characterized by complex visual hallucinations in individuals with visual impairment. We present the case of a patient with bilateral optic atrophy secondary to obstructive hydrocephalus caused by a pineal parenchymal tumor of intermediate differentiation (PPTID) who experienced formed visual hallucinations consistent with CBS. Following a right occipital craniotomy for occipital transtentorial approach and tumor resection, she developed elementary visual hallucinations. A thorough clinical history and systematic diagnostic evaluation led to the identification of coexisting right occipital epilepsy. This case highlights an intriguing overlap of two positive visual phenomena with distinct pathophysiological mechanisms.

1. Introduction

Charles Bonnet first described Charles Bonnet Syndrome (CBS) in the 18th century as a visual phenomenon occurring in those with visual impairment [1]. The term was coined much later by Morsier in 1967 [2]. A lesion in the occipital lobe is associated with loss of vision and elementary hallucinations. In contrast, a lesion in the parieto-occipital or temporo-occipital association cortex might present with complex visual hallucinations. CBS is also associated with ophthalmic pathologies and optic nerve dysfunction, where the hallucinations are more vivid and complex [3,4].

2. Case Presentation

55-year-old female with a history of pineal parenchymal tumor of intermediate differentiation (PPTID) leading to obstructive hydrocephalus, secondary to bilateral optic atrophy, and legal blindness. She would frequently see the images of people and animals in clear consciousness attributed to her visual loss. These events usually lasted a couple of hours and happened daily or more than once a day. She was seen by a neuro-ophthalmologist and was diagnosed with CBS, based on the clinical description of her visual symptoms and very low visual acuity of counting fingers. The brain magnetic resonance imaging (MRI) showed obstructive hydrocephalus due to compression of the third ventricle. A routine 20-minute electroencephalogram performed before the surgery was normal. After an initial decompression with external ventricular drainage (EVD) placement, she underwent elective right occipital craniotomy with occipital transtentorial approach for tumor resection. Two months after the resection, she started to experience a new intermittent visual phenomenon. She described seeing a multicolored nest or ball moving in her left visual hemifield. These episodes lasted 2–3 min each, and she was fully aware of herself and her surroundings during these events. She was experiencing 20–25 short visual spells each day without any apparent triggers. She was seen in the clinic due to these frequent visual spells, which were very distressing. Her neurological exam was intact except for a severe visual acuity deficit in both eyes. Brain Magnetic Resonance Imaging (MRI) revealed post-surgical changes and a small encephalomalacia in the right occipital region (Fig. 1). The patient was started on Levetiracetam and Valproic acid, with mild improvement in the frequency of these episodes. The patient was admitted to the epilepsy monitoring unit, where six typical focal aware seizures were captured. She described the seizures as visual hallucinations consisting of a nest or ball of fire in her left visual hemifield, lasting 2–3 min each, without alteration in consciousness. Ictal EEG showed evolving patterns of rhythmic alpha and theta superimposed by epileptiform discharges in the right temporo-occipital region. A few seizures evolved to the contralateral left occipital region (Fig. 2, Fig. 3). The antiseizure medications (ASMs) were re-started on the day before discharge from EMU, and the focal aware seizures subsided. However, the patient presented complex visual hallucinations consisting of colored animals, which lasted more than three hours on the last day of admission. These complex visual hallucinations did not respond to treatment with ASMs and were not associated with any EEG ictal changes. The patient recognized and mentioned the differences between the two phenomena. This later finding agrees with the idea that visual hallucinations seen in CBS are not due to epileptic discharges but likely due to the deafferentation of visual signals to the occipital cortex.

Fig. 1.

Brain Magnetic Resonance Imaging (MRI) with radiographic gross total resection of the pineal tumor, with some encephalomalacia in the right occipital region along the surgical corridor (arrow).

Fig. 2.

a: Seizure 1 onset in right temporo-occipital region (arrow).

Fig. 3.

a: Seizure 2 Onset in the right temporo-occipital region (arrow).

A Positron Emission Tomographic (PET) brain scan showed mild right occipital hypometabolism (Fig. 4). The patient was diagnosed with focal right occipital lobe seizures. The antiseizure medications were adjusted: Zonisamide, Levetiracetam, and Lacosamide, with improvement in her seizure frequency to once every other day. This case was discussed in the epilepsy surgery conference to assess her candidacy for surgery as her visual acuity is significantly impaired.

Fig. 4.

Positron emission tomography (PET) scan axial view showing mild right occipital hypometabolism (arrow).

3. Discussion

We report a case initially diagnosed with CBS due to severe vision loss in the setting of PPTID, hydrocephalus, and secondary bilateral optic atrophy. Visual hallucinations were described as complex visual phenomena, such as seeing people or animals for hours. Two months after the tumor resection, she presents with a new visual phenomenon of elementary visual hallucinations. Although it was initially suspected that this could be a part of the CBS, the latest visual hallucinations were stereotypical, occurring in the same visual field, and were shorter than before, lasting 1–2 min. These episodes occurred multiple times per day and caused distress. Both the description of her symptoms and the close relationship with recent brain surgery raised the suspicion of a different pathological process, leading to further evaluation and diagnosis of right focal occipital lobe epilepsy. To our knowledge, this is a rare case with two different pathologies presenting similar symptomatology of visual hallucinations. The Pathophysiology of CBS is understood as a phantom vision phenomenon due to deafferentation in the setting of vision loss [5]. Previous studies suggest that social isolation and neurocognitive deficits contribute to the development of CBS in persons with visual impairment [6,7].

Seizures involving the primary visual cortex can present with visual aura and elementary visual phenomena such as unformed images and patterns, as seen in this case. These focal sensory visual seizures can present as a positive phenomenon of seeing multicolored shapes, circles, and flashes or a negative phenomenon like visual blackouts or whiteouts [8]. The present patient did not have any alteration of consciousness during these seizures, consistent with focal aware seizures. On the other hand, seizures involving the visual association cortex can present with more vivid visual phenomena, such as seeing animals, faces, and people, and mimic CBS. Detailed evaluation is essential, as the management of these conditions is different. It becomes even more challenging when occipital seizures present comorbidly with CBS.

Treatment with three antiseizure medications reduced the seizure frequency to approximately once every other day. The patient is now aware of the differences in her visual hallucinations and can report the seizure frequency. Due to the intractability and distress that these seizures cause, the patient is being evaluated for possible resective epilepsy surgery.

4. Conclusion

This case reports a rare overlap of two distinct positive visual phenomena. A detailed description of visual hallucinations, neurological and ophthalmological examination, brain MRI, video-EEG, and PET scan allowed the diagnosis of focal aware seizures with elementary visual auras in a patient with complex visual hallucinations due to CBS.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.