Description
Hamartoma of tuber cinereum, also known as hypothalamic hamartoma, is a benign, congenital malformation involving the hypothalamus, particularly the tuber cinereum and mammillary bodies. These lesions consist of normal neuronal and glial tissue in an abnormal location.
Pathogenesis
The exact cause is unknown, but these lesions are generally believed to arise from embryonic neuronal ectopia, where neurons fail to migrate to their correct location during embryogenesis.
Epidemiology, Risk Factors & Associations
- Incidence: Rare (exact figures not well-established)
- No clear gender predilection
- Associated conditions: Gelastic epilepsy (laughter-induced seizures), precocious puberty, behavioural and cognitive impairments, and endocrine abnormalities (rare)
Clinical Features
The most common presentation is with gelastic seizures, often starting in early infancy. Other symptoms can include other types of seizures, cognitive or behavioural difficulties.
Precocious puberty is another feature characterised by:
- Breast development and menses in girls (before the age of 8)
- Increased testicular volume in boys (before the age of 9).
Complications
Potential complications can include treatment-related effects (from surgery, radiotherapy, or medication) and the impact of chronic epilepsy on mental and physical health.
Pathological Features
Histopathology
- Macroscopic: Usually small, round or oval, and greyish lesion attached to the floor of the third ventricle.
- Microscopic: Composed of dysplastic neurons and glial cells.
Radiological Features
General Features
- Characteristically demonstrates a well-defined, non-enhancing mass at the tuber cinereum on the floor of the third ventricle.
- May cause indirect signs of hydrocephalus due to obstruction.
CT
- Non-contrast: Iso- to slightly hyperdense compared to adjacent brain
- Contrast-enhanced: Usually non-enhancing
MRI
- T1: Iso- to hypointense compared to grey matter
- T2: Hyperintense
- T1 C+: Non-enhancing
- DWI/ADC: No restricted diffusion
- FLAIR: Hyperintense
Grading and Staging
Hamartomas are benign lesions and hence are not typically graded or staged.
Diagnosis
The diagnosis is typically based on the characteristic imaging features and clinical presentation. Histological confirmation is rarely required.
Differential Diagnosis
- Hypothalamic glioma: Gliomas are typically infiltrative and enhance on contrast administration, which helps to differentiate them from hamartomas.
- Craniopharyngioma: These are often calcified and demonstrate a variable pattern of enhancement.
- Pituitary macroadenoma: These generally originate from the sella turcica, extend into the suprasellar region and compress the hypothalamus rather than originate from it.
- Arachnoid cyst: Typically cerebrospinal fluid signal on all sequences, without the presence of dysplastic tissue.
- Rathke’s cleft cyst: Typically seen within the pituitary fossa and may have a variable MRI appearance, depending on the cyst contents.
Management
Management is multidisciplinary, involving neurologists, endocrinologists, and neurosurgeons. The mainstay of treatment is the control of seizures and endocrine abnormalities. Surgical resection or disconnection, radiofrequency ablation, gamma knife radiosurgery, and medical management have all been used.