MR imaging features in hypothalamic hamartoma: a report of three cases and review of literature.P Shah, D Patkar, T Patankar, J Shah, P Srinivasa, A Krishnan
Department of Radiology, Seth G. S. Medical College and K.E.M Hosital, Parel, Mumbai, India. , India
Hypothalamic hamartomas are rare tumours of particular interest because of their unusual symptoms. Three cases of hypothalamic hamartomas are reported in children, who presented with precocious puberty and gelastic seizures.
Keywords: Adolescent, Case Report, Child, Female, Hamartoma, diagnosis,Human, Hypothalamic Diseases, diagnosis,Male,
Hypothalamic hamartomas represent neoplastic proliferation of well-organised brain tissue similar to heteropias. Classical location and magnetic resonance imaging (MRI) features strongly favour the diagnosis. We report three cases of hypothalamic hamartomas who presented with precocious puberty and gelastic seizures.
A six-year-old girl presented with episodes of epileptic laughters (Gelastic seizures) 20 to 30 times a day since two years. Clinically her sexual characters were well ahead of those expected for her age. Laboratory studies and endocrine studies were normal. Radiologically bone age was normal for her age. Axial MRI showed a well-circumscribed isointense mass in the region of hypothalamus [Figure - 1]. Coronal scans demonstrated contiguity between the mass and the tuber cinereum. The mass did not enhance after instillation of gadolinium. In view of the clinical findings and imaging findings on MR, a diagnosis of hypothalamic hamartoma was considered. Patient was started on medroxy progesterone acetate. A follow up MRI after 6 months did not show any obvious change in the size or the morphology of lesion.
A 14-year-old girl presented with precocious puberty and delay, in neurological development. Past history revealed one episode of generalised convulsion at the age of two years. At the age of four years facial pimples were observed. Her height and weight were 2.5 S.D. more for her age. Neurological examination was normal. Laboratory investigations were unremarkable. Plain films of the skull were normal. MRI demonstrated a round well-marginated soft tissue mass isointense to grey matter in region of the hypothalamus [Figure - 2] No enhancement was seen on the post-gadolinium MR images. A diagnosis of hypothalamic hamartoma was considered. Patient responded well to medical management with medroxy progesterone acetate.
A 12-year-old boy presented with history of gelastic seizures starting at age of nine years. He also gave history of frontal headache, fatigue, anorexia and irritability since one year. Neurological examination was normal. The bone age was approximately 14 years. MRI showed isointense mass situated eccentrically in hypothalamus surrounded by cerebrospinal fluid (CSF).
There was no enhancement on post contrast scans. A diagnosis of hypothalamic hamartoma was considered based on typical grey matter intensity and lack of enhancement. Patient responded well to medical management with medroxy progesterone acetate.
Le marquand and Russell were the first to report hypothalamic hamartornas as congenital malformations consisting of tumour like collections of normal brain tissue lodged in an abnormal location.
Hamartomas are not true neoplasms. Pathologically they contain the nerve cells that resemble those of the tuber cinereum along with normal glial cells. Most of these lesions occur in hypothalamus. Other reported locations may be the subcortical cerebral cortex and periventricular region.
Hypothalamic hamartomas are small pedunculated growths contiguous with posterior hypothalamus, between the tuber cinereum and mamillary bodies. They fill the free space between the optic chiasm and pons and usually do not distort the hypothalamus or other parts of the base of the brain unless they are very large.
They occur with equal frequency in males and females. Most of patients usually present in the first or second decade of life. These patients typically present with precocious puberty. [35-70%] although the mechanism for this is not well understood. It may be from premature disappearance of normal inhibitory factors on hypothalamus, which results in luteinising hormone releasing factor (LHRH) being released prematurely thus activating the pituitary gonadal axis. The larger hamartomas are less likely to produce precocious puberty.
Occasionally, visual disturbances may be present because of involvement of optic pathways. Other presenting symptoms may also include seizures and/or laughing spells. On imaging, hypothalamic hamartomas produce characteristic soft tissue masses iso-intense to grey matter. They are homogeneous and sharply marginated by the surrounding CSF, as they do not cross the blood brain barrier they do not show enhancement on post-contrast images. Calcification is rare and haemorrhage is not described in these lesions. The anatomic location of these hamartomas together with signal intensity similar to grey matter on T1 WI and a higher intensity than gay matter on PDWI and T2 WI strongly, supports this diagnosis. All our patients showed classical well-marginated soft tissue masses of grey, matter in intensity in region of hypothalamus and no enhancement on contrast. The diagnosis was made on the basis of the characteristic location, isointensity to normal brain and lack of contrast enhancement. Follow up MRI in one of our patients showed no change in size and morphology of the mass.
Differential diagnosis of hypothalamic hamartoma may include craniopharyngioma, optic gliomas hyothalamic gliomas and gangliogliomas. All these tumours enhance after contrast. Calcification is common in craniopharyngiomas and optic gliomas Hypothalamic gliomas although a close differential are usually, inhomogeneous and often show enhancement. Rarely, enhancement in hypothalamic hamartomas has been reported in patients with neurofibromatosis. In cases of hypothalamic hamartomas surgical treatment is not always favourable. Medical treatment with medroxy progesterone acetate is the treatment of choice in most patients. Follow up MRI is recommended every six to 12 months for demonstrating lack of growth.
In conclusion, hypothalamic hamartomas are rare congenital malformations. Classical clinical presentation of isosexual precocious puberty, alone, with MR imaging features of isointense non-enhancing, mass of the grey matter intensity in the region of the hypothalamus is highly, suggestive of the diagnosis.
[Figure - 1], [Figure - 2], [Figure - 3]