CASE 12342 Published on 11.02.2015

Leptomeningeal cyst in a adult: a rare incidental finding

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Arribas García, J*; Blanco Cabellos, JA*; Ossaba Vélez, S*; Galobardes, J*

Hospital Infanta Cristina (Parla, Madrid).
Unidad Central de Radiodiagnostico
Patient

69 years, male

Categories
Area of Interest Neuroradiology brain ; Imaging Technique MR
Clinical History
Incidental finding in a cerebral MRI study.
Imaging Findings
Our patient is a 69-year-old man. As an incidental finding, we found a temporal area of parenchymal gliosis (Fig. 1, 2). It was associated with an extraaxial small collection hypointense on T1 and hyperintense on T2 without significant contrast enhancement. The bulge was protruding through a temporal skull defect (Fig. 3).
Discussion
Leptomeningeal cysts or growing skull fractures are a complication in head trauma in the paediatric population. They occur only in a 0.6 % of skull fractures [1]. In adults they are very rare. They are caused by a progressive enlargement of a fracture due to an underlying tear of the dura. A dural tear with CSF pulse and pulsation of the brain can cause CSF to collect inside the trapped leptomeninges forming a cyst. Mechanical stress can cause also bone erosion and widening at the fracture site. In some cases CSF advance through the bone margins of the fracture to the subcutaneous plane and eventually a palpable mass in the soft tissue is detected [2, 3]. The parietal and temporal bones are the most commonly implicated sites. Sometimes growing skull fractures spontaneously stabilize. CT is useful to assess bone and MRI is more accurate in demonstrating the brain damage.

MRI findings are usually consistent with a cystic lesion of CSF associating a bone defect in the skull and gliosis in the underlying brain parenchyma.

Differential diagnosis is important in order to decide whether biopsy, surgical intervention or follow-up is required. Intradiploic arachnoid cyst may show bone scalloping but no associated skull defect. Lesions causing bone defects may be congenital (dermoid/epidermoid, cephalocele), posttraumatic (leptomeningeal cyst) and iatrogenic (pseudomeningocele). Epidermoid cyst may involve both the inner and the outer tables of the skull and demonstrate marked hyperintensity on DWI. Cephaloceles are herniations of the brain due to congenital fusion defects, they are usually seen in the occipital region in newborns. Pseudomeningoceles are the herniation of CSF or brain parenchyma into the subcutaneous tissue due to a postoperative bone defect.

At the moment surgery is the treatment of choice and removal is recommended to prevent complications.

The post-traumatic leptomeningeal cyst in the adult population is very rare with few cases reported. Our patient was asked for head trauma antecedent in childhood referring eventually some hit on the head, "like all the children", not particularly strong. Although rare, we can find a leptomeningeal cyst in adults.
Differential Diagnosis List
Leptomeningeal cyst in an adult.
Intradiploic arachnoid cyst
Epidermoid
Cephalocele
Final Diagnosis
Leptomeningeal cyst in an adult.
Case information
URL: https://www.eurorad.org/case/12342
DOI: 10.1594/EURORAD/CASE.12342
ISSN: 1563-4086