Rationale:
To describe the clinical presentation and symptom trajectory of a possibly unique perceptual-cognitive complication of hippocampal laser interstitial thermal therapy (LITT) for refractory focal epilepsy.
Methods:
A 44-year-old left-handed Caucasian female was evaluated for a medically refractory epilepsy. Seizures were characterized by an aura of body ‘chill’ followed by fumbling movements and confusion, with limited post-ictal recall of events. MRI brain revealed left hippocampal sclerosis (Figure 1). Interictal EEG showed intermittent left temporal slowing, with ictal rhythms diffusely left hemispheric. FDG-PET showed widespread left hemispheric hypometabolism, most significant in the mesial temporal region. Despite some atypical features for a conventional mesial temporal epilepsy, the patient stated her preference for laser ablation of the left hippocampus, which was carried out uneventfully (Figure 2).
Results:
Postoperative visual field examination revealed right upper quadrantanopia. Two days post-procedure, the patient’s spouse reported her seeing things that ‘were not there’: ‘fireworks, old ladies walking, flags blowing, cars, purses and many more objects’. Cranial CT showed only the expected changes of swelling in the left medial temporal region. The patient’s hallucinations continued for several weeks, subsiding gradually thereafter. Hallucinations comprised human faces (including, ironically, a woman wearing a bonnet), simple shapes, and moving objects such as bicycles in her amblyopic field. Mood, affect and thought content remained intact. Six months following LITT the patient has occasional brief auras but is free of major seizures. Visual field examination remains unchanged. Interval cranial MRI with diffusion tractography of the visual pathways is awaited. Described in 1760, the Charles Bonnet syndrome denotes formed visual hallucinations provoked by visual deprivation (Carpenter et al. (2019), Ophth Physiol Opt 39(6):414-421). It is a rare complication of neurosurgical procedures in the posterior cortex; even rarer is the syndrome occurring due to interruption of Meyer’s loop following conventional anterior temporal lobe resections (Freiman TM, et al. (2004); J Neurosurg 101(5):846-53).
Conclusions:
To our knowledge, this is the first report of Charles Bonnet syndrome following hippocampal LITT. The patient’s rationality of thought, in addition to the preferential location of hallucinations in her blind field excluded the alternative diagnosis of a de novo psychosis that may also complicate anterior temporal lobectomy (Calvet et al. (2011), Ep Behav 22(4):804-7).
Funding:
Wilder family endowments to the University of Florida and NINDS R21NS128503 to GPK