Harlequin sign due to an upper thoracic paravertebral lesion. A systematic review of the literature

Introduction: Harlequin syndrome (HS) is an uncommon condition affecting the sympathetic nervous system, characterized by asymmetrical flushing and sweating impairment, which can affect the face or half of the body. When the dysfunction results from external factors like damage or compression, it's referred to as Harlequin Sign. Our objective was to document an exceedingly rare presentation of Harlequin Sign caused by a T3-T4 paravertebral mass and conduct the first systematic literature review on this subject.

Methods: We conducted a systematic review of English-language studies using PubMed, Scopus, and Embase databases. We excluded abstracts, posters, congenital and idiopathic Harlequin Syndrome cases, as well as iatrogenic and secondary Harlequin Sign cases related to pathologies other than upper thoracic lesions.

Results: We employed the PRISMA protocol and reviewed 1,538 papers, identifying 8 single case reports describing the Harlequin sign resulting from upper thoracic paravertebral lesions. The mean age of the patients was 41.25 years, with 6 (75 %) being female. The average time from onset to presentation was 8 months, and all patients (100 %) exhibited hemifacial flushing, while 4 (50 %) also had hemifacial anhidrosis. Stress or exercise exacerbated these symptoms in 50 % of cases. Additionally, 3 patients (37.5 %) presented with associated Horner Syndrome. The most commonly used diagnostic tool was a CT scan (50 %), revealing an average tumor diameter of 3.95 cm, with 50 % of cases located at T2-T3. Diagnosis indicated 57 % of cases as schwannomas and 29 % as lung adenocarcinoma (Superior Sulcus). Unfortunately, surgical treatment resolved symptoms in only 25 % of patients.

Conclusions: Hemifacial or hemibody autonomic symptoms should raise concern for paraspinal lesions in the thoracic spine. In addition to the first comprehensive review on this topic, we present a rare case of a T3/4 paraspinal schwannoma causing Harlequin Syndrome successfully managed with neurosurgical intervention.