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To the Editor: While there is no specific diagnostic test for Parkinson disease (PD), recent studies using iodine 123–metaiodobenzylguanidine (MIBG) have shown that cardiac sympathetic innervation is reduced in patients with PD.^1-2 -Synuclein aggregations are found in the sympathetic ganglions as well as in the midbrain dopaminergic neurons.³ It is possible that sympathetic innervation to the pupillary dilator muscle in PD is reduced because it is innervated by the cervical sympathetic ganglia. We studied sympathetic dysfunction in the pupils as a possible diagnostic marker of PD by comparing responses to cocaine eye drops and phenylephrine eye drops. Cocaine blocks norepinephrine uptake, and cocaine-induced mydriasis is dependent on the sympathetic nerve terminal density. In contrast, phenylephrine acts directly on the adrenergic receptor to cause mydriasis.

Methods

Participants included patients with PD (according to the criteria of the United Kingdom Parkinson’s Disease Society Brain Bank⁴), controls (patients reporting symptoms including headache, . . . [Full Text of this Article]

Hideyuki Sawada, MD, PhD; Kentarou Yamakawa, MD; Hodaka Yamakado, MD
Department of Neurology
Kyoto University Hospital
Kyoto, Japan

Ryohei Hosokawa, MD, PhD; Muneo Ohba, MD
Department of Cardiology
Kyoto University Hospital

Kazuaki Miyamoto, MD, PhD
Department of Ophthalmology
Kyoto University Hospital

Takashi Kawamura, MD, PhD
Kyoto University Center for Student Health

Shun Shimohama, MD, PhD
i53367@sakura.kudpc.kyoto-u.ac.jp
Department of Neurology
Kyoto University Hospital