Ruptured intracranial dermoids: magnetic resonance imaging.
D Patkar, A Krishnan, T Patankar, S Prasad, J Shah, J Limdi
Department of Radiology, Dr. Balabhai Nanavati Hospital, Mumbai, India., India
Department of Radiology, Dr. Balabhai Nanavati Hospital, Mumbai, India.
Rupture of intracranial dermoids tumour is rare and carries with it the risk of significant morbidity as well as fatality. Three cases that presented with varying symptoms ranging from headache to chiasmatic compression and suspected to have rupture of dermoid tumour are described. The importance of MR imaging in their diagnosis is discussed.
|How to cite this article:|
Patkar D, Krishnan A, Patankar T, Prasad S, Shah J, Limdi J. Ruptured intracranial dermoids: magnetic resonance imaging. J Postgrad Med 1999;45:49-52
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Patkar D, Krishnan A, Patankar T, Prasad S, Shah J, Limdi J. Ruptured intracranial dermoids: magnetic resonance imaging. J Postgrad Med [serial online] 1999 [cited 2019 Dec 14 ];45:49-52
Available from: http://www.jpgmonline.com/text.asp?1999/45/2/49/351
Intracranial dermoids are rare tumours of congenital origin accounting for less than 1% of all intracranial tumours; rarely these tumours may rupture either spontaneously during or following surgery or rarely following head trauma. They may either be totally asymptomatic or present acutely with a plethora of symptoms. Early magnetic resonance imaging (MRI) is essential to provide a preoperative diagnosis for prompt surgical intervention.
A thirty-year-old male presented with insidious onset of diminished vision in both the eyes over a period of two months. In the last few days he had become irritable and had to be admitted for severe headache and vomiting. Neurological examination demonstrated bitemporal hemianopsia. T1 weighted MRI of the brain revealed a mixed intensity non-homogeneous mass in the suprasellar region displacing the optic chiasma superiorly. [Figure:1A]. The mass showed a hypointense [Figure:1B] component along with a large lipid hyperintense component [Figure:1C]. There were multiple small hyperintense lesions in the right Sylvian fissure suggesting fat droplets. On the basis of the clinical presentation and the radiological images, a diagnosis of ruptured intracranial dermoid was made. At surgery, a dermoid cyst with contents was evacuated. Fat was found at various locations especially in the sylvian fissures and cisterns adherent to the dura and cerebral surface. Post-operatively, the patient showed significant improvement in the clinical status.
A twenty-five-year old female patient was admitted for generalized tonic clonic seizures. Clinical and neurological examination revealed an agitated but alert individual complaining of headaches. Motor and sensory examination was within normal limits. T1 weighted MR imaging showed a lobulated non-homogeneous hyperintense lesion in the subfrontal area [Figure:2]. Also, fat droplets were seen in the perimesencephalic and parasellar cisterns as well as in other spaces. A preoperative diagnosis of ruptured dermoid cyst was made. On surgery the dermoid cyst was evacuated. The patient has been followed up uneventfully for the past one year.
A twenty-year-old male patient had been suffering from periodic headaches and occasional seizures for the past one year, which had increased in frequency. On T1 weighted MR imaging, a large suprasellar, lobulated hyperintense mass medial to the left temporal lobe was identified [Figure:3]. Hyperintense fat droplets in the left Sylvian fissure were also noted. The diagnosis was confirmed on exploration and the dermoid was excised. The patient is asymptomatic since the last one year.
Intracranial dermoids are uncommon and originate from ectodermal inclusions of primitive pluripotent cells due to defects in closure of neural tube at around three to five weeks of gestation. They are usually found in the midline in contrast to epidermoids. Some common locations include the parasellar, frontobasal region and the posterior fossa. They are composed of a thick fibrous capsule with a lining, of stratified squamous epithelium enclosing a thick viscous greenish brown fluid. This fluid comprises lipid metabolites, liquid cholesterol, whorls of hair, calcifications and decomposed epithelial cells. Sometimes sebaceous or sweat glands are also present.
Patients with dermoid cysts may either be asymptomatic or present with headaches, seizures or signs of compression of neighbouring tissues. After rupture of these cysts, the fatty content of these tumours can disperse into the subarachnoid space and find itself in any of the cisterns and ventricles. Most often the rupture is spontaneous though in certain instances trauma, such as closed head injury has been implicated. Clinical manifestations in ruptured dermoid are very diverse. These include seizures, aseptic meningitis, transient cerebral ischaemia as a result of vasospasm and even olfactory delusion. Rarely intraventricular fat leads to rapidly developing hydrocephalus due to granuloma in the aqueduct. Computed tomographic (CT) findings are represented by the fat droplets in the subarachnoid spaces or a fat/fluid level within the ventricles. This is usually associated with an extra-axial or combined extra and intra-axial soft tissue mass representing the dermoid. The fat/fluid levels correlate with the extent of spread of the lipid contents of the cyst. Not all lesions are visualized as some dermoid cysts contain a lower proportion of fat and more of hair. On MRI the fat can be seen dispersed as strongly hyper-intense signals on T-1 weighted imaging while the other tumour contents appear hypo-intense. On T2 weighted imaging, the fat component turns slightly, hypo-intense similar to subcutaneous fat. Characteristically the tumour is often non-homogeneous due to its mixed composition. While both CT and MRI are sensitive, MR has some distinct advantages. In addition to allowing multiplanar imaging, the exact extent of the mass and its relation to the skull base can be more easily evaluated because of the lack of bone artefacts. Lastly, the capability of MR to evaluate the associated vessel displacement and mass effect on adjacent structures makes it the preferred technique.
In conclusion, MR plays a pivotal role in the diagnosis of rupture of intra-cranial dermoids. Prognosis of patients diagnosed with ruptured intra-cranial dermoids depends on the spread of the contents and the time period after rupture. Often symptoms do not correlate with the time of rupture and are a response to the cholesterol rather than lipid content. Mortality as well as morbidity from complications such as chemical arachnoiditis can be significantly reduced if imaging is done early in these patients.
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