Horner syndrome secondary to edema of the longus colli muscle: a case report

Background Horner syndrome is caused by disruption to any part of the oculosympathetic nerve supply, and is classically characterized by the triad of ptosis, miosis, and facial anhidrosis. Two cases of Horner syndrome secondary to longus colli edema have previously been reported in the literature; however, this is the first case of bilateral asymmetric longus colli inflammation causing unilateral Horner syndrome. Case presentation An 18-year-old male was found unresponsive in his car after a motor vehicle accident and was found to have new onset anisocoria with a miotic left pupil and left-sided ptosis consistent with Horner syndrome. Imaging was unremarkable except for the MRI neck soft tissues, which revealed abnormal increased signal intensity consistent with extensive edema in the left longus colli muscle and a shorter segment of edema in the right longus colli muscle. Conclusion The patient’s presentation and imaging results suggest Horner syndrome secondary to edema of the longus colli muscle, as the second-order sympathetic innervation to the eye runs under the longus colli. Traumatic Horner syndrome from longus colli contusion is a rare and benign entity that may self-resolve as inflammation and compression decrease. Imaging of the soft tissues of the neck is vital in assessing this rare occurrence. More common and concerning etiologies should be excluded with proper vascular, cerebral and spinal imaging before attributing Horner syndrome to a benign cause.