- Correspondence to Helen Williams, Radiology Department, Birmingham Children's Hospital, Steelhouse Lane, Birmingham, West Midlands B4 6NH, UK;
- Received 14 April 2012
- Accepted 18 April 2012
- Published Online First 26 July 2012
Answers to the following two quiz questions can be found on page 239
Theme: midline brain abnormalities
For each of the following questions select one option from the following:
Posterior pituitary ectopia
A 11-year-old girl presented with short stature and subsequent investigations revealed isolated growth hormone deficiency. A MRI scan was performed to look for any associated pituitary abnormalities. Figure 1 is a midline unenhanced, T1-weighted sagittal image of her brain. What does it show?
A 6-year-old boy underwent MRI scan as part of his investigation for rapidly progressing central precocious puberty. What is the diagnosis based on this midline unenhanced, T1-weighted sagittal image (figure 2)?
Answers to the questions from page 216
The correct answer is D; posterior pituitary ectopia (PPE). The posterior pituitary, which has high (bright) signal on T1-weighted sequences (sometimes referred to as the posterior pituitary ‘bright spot’) should be located behind the anterior pituitary in the pituitary fossa. In this case, it is ectopically located half-way down the pituitary stalk (arrow, figure 3). In PPE, the bright spot may be identified along the inferior surface of the tuber cinereum which is part of the hypothalamus, forming the floor of the third ventricle between the mamillary bodies (posteriorly) and the optic chiasm (anteriorly). In PPE, the pituitary stalk is often small or truncated and the anterior pituitary gland may be small.
Congenital abnormalities of the pituitary gland and stalk are often associated with hypothalamic-pituitary axis malfunction. They may also be seen as part of syndromes such as septo-optic dysplasia and Kallman syndrome. PPE is most commonly associated with short stature secondary to growth hormone deficiency, but multiple endocrine deficiencies can occur. Anomalies of other structures formed at the same time embryologically should be carefully looked for on any imaging performed; including the eyes, forebrain and olfactory bulbs. Patients with midline facial abnormalities have an increased incidence of midline and other congenital central nervous system abnormalities. In such patients, MRI scan of the brain can provide diagnostic and/or prognostic information.
The correct answer is G; hypothalamic hamartoma, sometimes referred to as a hamartoma of the tuber cinereum. There is a small rounded mass, isointense to grey matter on the undersurface of the tuber cinereum, between the mamillary bodies and the pituitary stalk (arrow, figure 4). Hypothalamic hamartomas are congenital, non-neoplastic collections of heterotopic neurones and glia originating from the hypothalamus. They present clinically with LHRH dependent central precocious puberty at a very young age and/or gelastic seizures. Some children present with partial complex epilepsy. A hypothalamic hamartoma is identified in up to one-third of patients with precocious puberty and they usually present between 1 and 3 years of age. They typically measure approximately 1 cm in diameter on imaging and do not change in size over time. Pedunculated lesions are less likely to be symptomatic, whereas sessile lesions are almost always symptomatic. Any lesion that shows signs of growth or enhances should be biopsied to exclude other pathology.
Competing interests None.
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