Closed-Eye Visualizations in the Setting of Hyponatremia

Purpose To report a case of closed-eye visualizations and to clarify the different types of hallucinations and their etiologies. Methods Retrospective case report of a patient with closed-eye visualizations secondary to hyponatremia. Clinical findings, physical exam, laboratory assessment, treatment, and disease course from the patient's hospitalization were used in creating this report. Follow-up data after discharge were also obtained. Results Closed-eye visualizations were diagnosed as secondary to hyponatremia, as they did not occur with the eyes open, and potential alternate causes were excluded. Serum sodium nadir was 119 mEq/L. Symptoms resolved with correction of hyponatremia via fluid resuscitation and electrolyte replenishment. There has been no recurrence of the symptoms. Conclusion This patient had hallucinations exclusively with the eyes closed, which must be differentiated from the release hallucinations seen with the eyes open in Charles Bonnet syndrome. This patient had no visual loss or retinal disease, which should be suspected in open eye hallucinations.


Introduction
A hallucination is the perception of an object or an event in the absence of an external stimulus. Visual hallucinations can be categorized as simple-lights, colors, or shapes-or complex with objects and people [1]. Causes include psychosis, drugs, delirium, Charles Bonnet syndrome, compressive tumors, migraines, and hypnagogic phenomena [2]. A unifying feature of these hallucinations is that they occur when the patient's eyes are open. A review of the literature shows that cases of closedeye hallucinations have been reported in postoperative patients who received general anesthesia or rarely in temporal lobe epilepsy [3]. e patient in this case had not received any drugs known to be hallucinogenic and did not have history of seizures or any evidence of seizure during hospitalization.
Hyponatremia can be de ned as a serum sodium concentration less than 135 mEq/L. is is a known cause of neurologic symptoms, typically at levels below 120 mEq/L. Of patients with serum sodium less than 120 mEq/L, 0.5% report hallucinations [4]. However, this is the rst reported case of visual hallucinations occurring exclusively with eye closure secondary to hyponatremia. It is critical to recognize these visualizations as a correctable symptom of an electrolyte abnormality.

Case Description
An 80-year-old male with hypertension and coronary artery disease presented with a three-day history of emesis and diarrhea, diagnosed as gastroenteritis. He endorsed dizziness and weakness but did not report any headache, blurry vision, paresthesias, or syncope. e patient also described a threeday history of complex visualizations involving a moving car. e car had color and appeared life-like. It was not distorted and seemed to be driving in a realistic manner in front of him. is occurred exclusive when his eyes were closed and immediately resolved upon opening his eyes. It was present for the majority of the time his eyes were closed and made it di cult for him to sleep.
He denied any prior hallucinations and had insight that the car was not real. He had no history of head trauma, cerebrovascular disease, or personal or familial history of psychosis or dementia. Ophthalmologic history was unremarkable and he used glasses only for reading. He was not experiencing any other sensory hallucinations or illusions at this time.
e patient was hemodynamically stable and afebrile, and physical examination was signi cant only for mild abdominal tenderness.
ere were no signs of cognitive impairment. Fundoscopic examination did not reveal any abnormalities. Laboratory analysis showed white blood cell count 4.6 billion cells/L, sodium 119 mEq/L, potassium 3.2 mEq/L, carbon dioxide 24.6 mEq/L, anion gap 10, glucose 186 mg/dL, and lactate 2.1 mmol/L. Urine drug screen was negative. Chest X-ray was normal, and electrocardiogram showed normal sinus rhythm. Fluid resuscitation with normal saline and electrolyte replenishment was initiated. e visualizations decreased in frequency over the next two days and were completely absent by the third day after admission, which was the sixth day since they rst began. Serum sodium increased during treatment and was 130 mEq/L on the day the hallucinations subsided. e patient was discharged the next day and has not experienced any recurrence of closed-eye visualizations or other hallucinations in the eight months since.

Discussion
Visual hallucinations are often the manifestation of underlying neurologic or ophthalmologic pathology. In these patients, it is critical to take a thorough history including whether the visualizations are simple or complex, speci c content, presence of distortion, association with speci c triggers, and whether the patient has insight into their reality. ese details allow for the broad di erential of hallucinations to be narrowed to speci c causes. e mechanism behind hallucinations in hyponatremia is unclear, but the etiology of visual hallucinations in general can be grouped into three categories: brain anatomy, brain chemistry, and emergence of the unconscious into the conscious [5]. Both brain anatomy and brain chemistry could be a ected by electrolyte abnormalities. It is known that cerebral edema and intracellular swelling play a role in the central nervous system symptoms of hyponatremia [4]. e neurons in the visual cortex could also become more excitable through alterations in membrane potential. One of the leading theories regarding hallucinations is that they are due to an imbalance between inhibitory and excitatory inuences on the brain [6]. It has been theorized that, in susceptible patients, the temporary visual deprivation of eye closure could be enough to cause spontaneous ring of the visual cortex due to lack of visual inputs [7].
is case illustrates the importance of determining whether visualizations are seen with eyes opened or closed. Visual release phenomena, such as those seen in Charles Bonnet syndrome, occur exclusively when the eyes are open. ese patients most likely experience spontaneous ring of the visual cortex as a result of visual deprivation and dea erentation of visual cortical pathways [1].
ere is typically no underlying psychiatric disease, and the patients are aware that what they are seeing are hallucinations [8].
e patient in this case report could have been diagnosed with this syndrome if it was not speci cally elicited whether visualizations were present with eyes opened or closed, as the patient did not volunteer this information. It was crucial that this patient's symptoms were di erentiated from Charles Bonnet syndrome, as this would have prompted an unnecessary ophthalmologic workup. e symptoms experienced by the patient in this case are also phenomenologically similar to hypnagogic hallucinations. It is estimated that approximately 70% of the population experiences hallucinations at least once while transitioning from wakefulness to sleeping [9]. ese are involuntary and typically complex, featuring bright colors and people or objects. e person experiencing these perceptions is fully aware that they are not real and rarely is a ected emotionally by them [9]. is description ts the moving car visualized by our patient and his reaction to it. Hypnagogic hallucinations are thought to be due to increased cortical and thalamic activation, potentiated by acetylcholine in sleep, combined with spontaneous discharges resulting from cortical dea erentation [10]. It is possible that hyponatremia is another mechanism whereby the excitatory in uences on the brain may become out of proportion to inhibitory in uences.
is case documents a previously unreported symptom of hyponatremia, an exceedingly common problem in hospitalized patients. e correction of serum sodium is the only treatment necessary in cases of hallucinations, as this was su cient to cure this patient's symptoms. Further workup and treatment can be avoided unless symptoms persist or there is evidence of alternate etiologies. Patients can also be reassured that the visualizations will be temporary.