Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2022;12(3):e2022093 1 Dermatology Practical & Conceptual Square-shaped Alopecia After Embolization of Intracranial Aneurysm: a Case Report and Review Jorge Román-Sainz1, Nicolás Silvestre-Torner1, Fernando Gruber-Velasco1, Belen Romero-Jiménez1, Alejandro Lobato-Berezo2, Adrián Imbernón-Moya1 1 Department of Dermatology, Hospital Universitario Severo Ochoa, Leganés, Madrid, Spain 2 Department of Dermatology, Hospital del Mar-Parc de Salut Mar, Barcelona, Spain Key words: Alopecia, radiation, trichoscopy, intracranial aneurysm Citation: Román-Sainz J, Silvestre- Torner N, Gruber- Velasco F, Romero- Jiménez B. Square-shaped alopecia after embolization of intracranial aneurysm: case report and review. Dermatol Pract Concept. 2022;12(3):e2022093. DOI: https://doi.org/10.5826/dpc.1203a93 Accepted: October 15, 2021; Published: July 2022 Copyright: ©2022 Román-Sainz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (BY-NC-4.0), https://creativecomm ons.org/licenses/by-nc/4.0/ which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding author: Jorge Román Sainz, MD, Travesía de Téllez 8, 7º R. CP: 28007, Madrid, Phone: 680653019, E-Mail: jorgesheldon@gmail.com Introduction Endovascular interventional procedures are widely used for intracranial arterial pathologies treatment. They require realization of fluoroscopy, a technique that relies on X-rays to obtain real-time images [1]. Many cases of transient alopecia after this procedure have been reported. Case Presentation A 45-year-old male was admitted with an intracranial hemor- rhage after a rupture of an aneurysm in the anterior commu- nicating artery. Two embolization procedures were required. After 2 weeks, he experienced a partial hair loss, comprising the left temporoparietal scalp region. A 7,5-cm sized alope- cia plaque with angular edges and rectangular morphology was observed (Figure 1). Pull test was positive. Trichos- copy showed black dots and short vellus hairs (Figure 2). Lack of peladic hairs ruled out alopecia areata. Skin biopsy revealed multiple pilosebaceous units with obliterated follicles without signs of fibrosis. After 2 months the patient showed complete hair regrowth without treatment. Conclusions Transient radiation alopecia (TRA) is an adverse effect, which usually appears with accumulated doses between 3-6 Gy. Greater doses than 6 Gy may cause scarring alopecia [1,2]. This is caused by the simultaneous entry of multiple follicular cells in catagen phase. The dose of radiation produced by a fluoroscopy unit is usually between 0.02-0.05 Gy/min. Fifty-eight cases of TRA have been reported after intra- cranial arterial embolization, being more frequent in women, with a ratio of 1.41:1. The age varies from 13 years to 70 years, but most of the patients were between 30-50 years. Patients report sudden hair loss, producing plaques of alope- cia whose size and shape vary depending on the model of the device used. The characteristic angular edges and the medical history are essential for the differential diagnosis with alope- cia areata [1,2]. 2 Research Letter | Dermatol Pract Concept. 2022;12(3):e2022093 Figure 1. Alopecia area in the patient left temporoparietal region. Note the angular edges which give it a perfectly square contour. Figure 2. Trichoscopy performed on the edge of the alopecia area. Black dots can be observed, as well as short vellus hair. Research Letter | Dermatol Pract Concept. 2022;12(3):e2022093 3 The cumulative radiation dose was in most cases greater than 3 Gy, with 92% of cases ranging between 3-6 Gy [1]. Only one case of scarring TRA has been reported [2]. In the case of our patient, we do not know the exact dose of radia- tion received, but a total dose greater than 3 Gy was estimated. In trichoscopy, the most common findings include black dots and yellow dots, followed by short, vellus hairs. Broken hairs and white dots are less common [2]. These findings can be observed in alopecia areata. However, exclamation hairs are often seen in the latter, a finding that is not pres- ent in TRA. Histological findings show anagen or catagen follicles lacking inflammatory infiltrate or scar tissue [2]. Differential diagnosis should be made mainly with alopecia areata, in which a peri- or intra-bulbar lymphocytic infiltrate with a “honey-comb” image is usually observed. Time from the embolization procedure to the onset of alopecia ranges from 1-8 weeks. Most cases spontaneously resolve between 2-6 months, with complete regrowth. In some cases, cryotherapy, topical corticosteroids, topical minoxi- dil and/or intralesional triamcinolone were applied, without significant differences compared to untreated patients [2]. TRA is a transient condition that resolves without the need of treatment. Given the increase of such interventional procedures in recent years, it is important to know this entity and differentiate it mainly from alopecia areata. It should also be considered adding this side effect to the informed consent of such interventions. References 1. Freysz M, Mertz L, Lipsker D. Temporary localized alopecia fol- lowing neuroradiological procedures: 18 cases. Ann Dermatol Venereol. 2014;141;15-22. DOI: 10.1016/j.annder.2013.09.655. PMID: 24461089. 2. Cho S, Choi MJ, Lee JS, Zheng Z, Kim DY. Dermoscopic findings in radiation-induced alopecia after angioembolization.  Derma- tology.  2014;229:141–145. DOI: 10.1159/000362810. PMID: 25171463.