From the Guidelines
Patients may see snakes due to visual hallucinations, which can occur from various causes, including Charles Bonnet syndrome (CBS) in visually impaired individuals, as supported by the most recent study 1 and 1. The hallucinations can be attributed to a cortical-release phenomenon resulting from a lack of afferent visual information, as explained in the study 1. Some key points to consider include:
- Recurrent, vivid visual hallucinations are a characteristic of CBS, as noted in the study 1.
- The hallucinations can occur in patients with reduced visual acuity, contrast sensitivity, or visual field loss, and can occur in patients with monocular vision loss, as stated in the study 1.
- Limited evidence suggests that techniques such as eye movements, changing lighting, or distraction may reduce hallucinations in some patients, and these self-management methods can be recommended, as mentioned in the study 1.
- A recent trial reported reduced frequency of hallucinations in subjects receiving inhibitory transcranial direct-current stimulation (tDCS), as noted in the study 1. It is essential to distinguish between CBS and other conditions that may cause hallucinations, such as Parkinson's disease, dementias, psychiatric disease, or medication side effects, as highlighted in the study 1. If someone experiences visual hallucinations of snakes, they should seek immediate medical attention, as this could indicate a serious underlying condition requiring prompt evaluation and treatment.
From the Research
Possible Causes of Hallucinations
- Patients may see snakes due to various medical conditions, including post-concussional syndrome 2 and Charles Bonnet Syndrome (CBS) 3, 4, 5.
- CBS is characterized by complex visual hallucinations, ocular pathology causing visual deterioration, and preserved cognitive status 4, 5.
- In some cases, hallucinations may be a manifestation of post-concussional syndrome, as seen in a patient who experienced visual hallucinations of snakes after a car accident 2.
Characteristics of Hallucinations
- Hallucinations in CBS can be vivid, realistic, and recurring, and may include seeing objects or creatures, such as snakes 3, 4.
- Patients with CBS typically retain insight into the unreal nature of their hallucinations, but may still experience distress 4, 5.
- Hallucinations can also occur in other medical and neuropsychiatric conditions, and not all patients with hallucinations are psychotic 6.
Treatment Options
- Antipsychotic agents, such as risperidone and quetiapine, and anticonvulsants, such as levetiracetam, may be effective in treating hallucinations in some cases 3.
- Donepezil has been reported to be successful in improving cognitive function and reducing hallucinations in a patient with CBS and Alzheimer's type dementia 4.
- Olanzapine therapy has also been shown to be effective in treating hallucinatory visions related to CBS 5.
- Accurate differential diagnosis is crucial in determining the most appropriate treatment for hallucinations 6.