Hirayama disease (HD) is a rare cervical flexion myelopathy associated with subclinical autonomic dysfunction (AD). Cardiovascular autonomic neuropathy (CAN), though uncommon, may predispose to perioperative instability. We report an 18-year-old male with HD undergoing cervical laminoplasty who developed profound post-induction and positional hypotension without compensatory tachycardia, despite normal preoperative bedside autonomic testing. Hemodynamics were was managed with vasopressors and targeted fluid therapy. Subsequent autonomic evaluation revealed early cardiovascular AD, with an Ewing battery score of 2.5. Heart rate variability (HRV) indicated sympathetic predominance with impaired parasympathetic modulation—findings suggestive of early CAN. This case highlights the presence of clinically silent cardiovascular AD in HD and its potential to cause significant anesthetic-related hypotension. Incorporating HRV analysis as a simple, non-invasive adjunct to conventional autonomic testing may improve preoperative risk stratification and guide anesthetic management in patients with HD.