====== Aneurysmal bone cyst ======

Aneurysmal [[bone cyst]]s (ABCs) are benign, expansile, nonneoplastic [[osteolytic]] lesions that may originate of any site of the [[skeleton]]. 

===== Epidemiology =====

They represent 1%-2% of primary bone tumors.

The spine can be affect up to 30% of the cases, leading to pain, neurological deficits, and pathological fractures in symptomatic patients. The incidence of craniocervical (occipito-C1-2) occurrence is not known.

Cranial ABCs are even more rare and represent 3%-6% of these unique lesions.

===== Diagnosis =====

Do multiple fluid-fluid levels on MRI always reveal primary benign aneurysmal bone cyst?
((Girolami M, Caravelli S, Persiani V, Ghermandi R, Gasbarrini A. Do multiple
fluid-fluid levels on MRI always reveal primary benign aneurysmal bone cyst? J
Neurosurg Sci. 2018 Apr;62(2):234-236. doi: 10.23736/S0390-5616.16.03794-2.
PubMed PMID: 29540050.
)).

===== Case reports =====

Jayakumar N, Ismail HMB, Mulay S, Ashwood N. Aneurysmal bone cyst in the
[[cervical spine]]. BMJ Case Rep. 2019 Oct 5;12(10). pii: e231870. doi:
10.1136/bcr-2019-231870. PubMed PMID: 31586961.

----

An 11-year-old girl with a lesion in the posterior aspect of the atlas, and a 28-year-old man with an important hydrocephalus and a posterior expansible lesion on the left side of his posterior fossa. Total resection was achieved on both lesions, with no surgical morbidity. Even though ABCs are nonneoplastic lesions, subtotal resection is associated with early recurrence. The knowledge of the anatomy of the region in order to achieve the occlusion of arterial feeders prior to surgical resection itself is the key point of the surgical strategy
((Joaquim AF, Giacomini L, Ghizoni E, Tedeschi H. Aneurysmatic bone cyst of the 
craniocervical region: Surgical technique. J Neurosci Rural Pract. 2014
Jan;5(1):55-8. doi: 10.4103/0976-3147.127874. PubMed PMID: 24741252.)).

The case of a 3-year-old girl who presented with an acute posterior fossa epidural hematoma after minor trauma. Imaging workup revealed a previously undiagnosed suboccipital ABC that appeared to have ruptured as a result of her trauma, leading to a life-threatening hemorrhage. To the authors' knowledge, a ruptured ABC has never before been presented in the pediatric literature. In this case report, the authors review the imaging findings, natural history, clinical course, and treatment of these rare lesions
((Garber ST, Riva-Cambrin JK. Occipital aneurysmal bone cyst rupture following
head trauma: case report. J Neurosurg Pediatr. 2015 Mar;15(3):272-5. doi:
10.3171/2014.9.PEDS14224. Epub 2015 Jan 2. PubMed PMID: 25555115.)).