In sighted individuals, pupillary constriction decreased monotonically for at least 30 min during exposure to continuous low-irradiance light, indicating that steady-state pupillary responses are an order of magnitude slower than previously reported. In the absence of rod-cone function, pupillomotor responses are slow and sustained, and cannot track intermittent light stimuli, suggesting that rods/cones are required for encoding fast modulations in light intensity. Here, we show that visual photoreceptors are required for normal pupillary responses to continuous light exposure at low irradiance levels, and for sustained pupillary constriction during exposure to light in the long-wavelength portion of the visual spectrum. To assess the relative contribution of melanopsin and rod-cone photoreceptors to the pupillary light reflex in humans, we compared pupillary light responses in normally sighted individuals (n = 24) with a blind individual lacking rod-cone function. In mammals, the pupillary light reflex is mediated by intrinsically photosensitive melanopsin-containing retinal ganglion cells that also receive input from rod-cone photoreceptors. The sensitivity of PCT, especially for all severities of disease, distinguishes it from other physiological phenotypes, which may make it useful as a potential biomarker. Additionally, increased PCT correlated with the presence of craniofacial autonomic symptoms, linking pupillary circuit dysfunction to peripheral trigeminal sensitization. We found significantly increased PCT in probable, episodic, and chronic migraine, compared to controls. We used edge-light pupil cycle time (PCT) as a probe of the pupillary light circuit in migraine, paired with clinical assessment of migraine characteristics, and compared these to non-headache controls. Though physiological differences exist between migraineurs and non-headache controls, true physiological biomarkers have been elusive, especially for the full clinical spectrum of migraine, inclusive of chronic, episodic, and probable migraine. Diagnosis is currently based on clinical diagnostic criteria. Migraine is a neurological disorder characterized by paroxysms of head pain accompanied by trigeminovascular system activation and autonomic dysfunction. Sudomotor impairment is prominent and should be the focus of symptomatic management however, clinicians should be aware of symptoms beyond the classic triad. The pattern of autonomic dysfunction in Ross syndrome is suggestive of a limited autonomic ganglioneuropathy. Cardiovagal and adrenergic functions were preserved in most patients. Anhidrosis progressed slowly over time and sudomotor dysfunction was predominantly (post)ganglionic. Well-circumscribed small areas of preserved sweating within areas of anhidrosis were observed in the majority of patients (88.5%). Distributions of anhidrosis encountered were segmental (n = 15), widespread (n = 7), and global (n = 4). Positive autoantibodies were found in a minority of patients often with unclear clinical significance. An associated autoimmune disorder was identified in one patient. Other commonly reported symptoms included fatigue, chronic cough, and increased urinary frequency. The most common initial reported manifestation was an abnormal segmental sweating response in 16 patients (described as hyperhidrosis in 12 patients and anhidrosis in 4 patients) while a tonic pupil was the initial manifestation in 10 patients. Twenty-six patients with Ross syndrome were identified. Standardized autonomic reflex testing was reviewed when available. We performed a retrospective chart review of all patients who underwent a thermoregulatory sweat test (TST) between 19 and had confirmation of the diagnosis of Ross syndrome by an autonomic disorders specialist. We sought to characterize the clinical presentation, associated autoimmune disorders, and autonomic profile in patients with Ross syndrome to further elucidate its pathophysiology. Ross syndrome is a rare disorder characterized by tonic pupils, hyporeflexia, and segmental anhidrosis.
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