A hallmark of Parkinson’s disease is facial akinesia with decrease in blink frequency (Karson, 1984). A markedly decreased blink frequency from nyctophobia, a fear of the dark, has not heretofore been reported.
Case Study: A 26-year-old right handed male presented with a 20-year history of phantasmagoria. Visual hallucinations of strangers appeared several to a hundred times a day, seconds to minutes in duration. These morbid images were horrific, of dead people or ghosts, suddenly appearing in his visual space, actively attacking real people. Examples included a little girl, decapitated, cradling her head in her arm or Freddy Krueger like apparitions, shooting, stabbing, strangling or maiming actual people who were within the patient’s visual field. He was able to differentiate between the hallucinations and real people, either from the context (a non hallucination would not be murdering someone else), or he would wait for the hallucinations to vanish, allowing him to then interact with the person who is actually there. The images were so disturbing to him that he fled his home state to run away from the hallucinations, but to his chagrin, they persisted. There were diurnal variations to his hallucinations, which were more frequent at night, or when he closed his eyes, and the fear of these has induced nyctophobia. In order to avoid these, he attempted to curtail closing his eyes or blinking. He had been treated with 9 different psychotropic medications, which had no effect on his hallucinations. Phenytoin was begun, and once therapeutic levels were achieved, all of his hallucinations resolved, as did his nyctophobia, with return to normal blink frequency.
Physical examination: Bilateral palmar erythema. Facial expression with decreased blink frequency, approximately 1/per minute, but not otherwise hypomimetic. Neurological examination: Cranial Nerve (CN) Examination: CN III, IV and VI: bilateral ptosis. Motor Examination: Normal tone without cogwheel rigidity. No bradykinesia. Drift Testing: Right upward-outward drift, right cerebellar spooning, and Abductor Digiti Minimi sign. Gait: Normal without instability or retropulsion. Reflexes: 1+ throughout. Hoffman Reflex: positive bilaterally. Other: Magnetic Resonance Imaging of brain with/without infusion: Normal. Five-day Electroencephalogram: Temporal Lobe Status Epilepticus with bilateral foci.
In this individual, the sheer terror of phantasmagoria with his eyes closed, forced him to maintain them in the open position as long as possible, reducing his blink frequency to once a minute or less. The return to a normal rate of blink frequency with treatment using phenytoin, with resolution of his horrific hallucinations, further validates this as the origin for his infrequent blinking. In those with low nictation, without other manifestations of Parkinson’s disease, query as to volitional inhibition of blink frequency and nyctophobia is warranted.