lunedì 22 settembre 2008
Congenital ectopia of the posterior pituitary with anterior pituitary hypoplasia
Along the tuber cinereum, a 5 mm hyper intensity is noted on precontrast T1 images. The area shows homogenous, hyper intense signal on post contrast sequences. The pituitary infundibulum is threadlike and midline. The anterior pituitary gland is hypoplastic and located in the sella. It shows homogenous enhancement.
- Ectopia of the posterior pituitary
- Rathke cleft cyst
- Langerhans cell histiocytosis
Diagnosis: Congenital ectopia of the posterior pituitary with anterior pituitary hypoplasia
Ectopia of the posterior pituitary is a rare congenital anomaly. The anterior pituitary is often hypoplastic. Patients often will present with panhypopituitarism and short stature secondary to growth hormone deficiency. Those patients with a visible pituitary stalk typically present with isolated growth hormone deficiency. On the other hand, those with absent pituitary stalks will present with multiple hormonal deficiencies. Hypopituitarism has been associated with breech delivery, genital abnormalities, hypoglycemia, single central incisor and jaundice. Even if not initially present, complete anterior pituitary hormone deficiency can develop during a patient's teens or twenties.
MRI is the imaging modality of choice to study the anatomic relationships that exist in the pituitary-hypothalamic region. Both pre and post contrast T1 weighted images should be obtained. The best imaging planes are sagittal and coronal. Fat suppression imaging can also be useful as the bright signal associated with the posterior pituitary will not typically suppress.
Located in midline at the median eminence, the ectopic posterior pituitary gland will either be T1 hyper intense or isointense on precontrast images. It is posterior and inferior to the optic chiasm. On post contrast images, it will appear hyper intense. The sella will either be hypoplastic or completely absent. Similarly, the anterior pituitary will be hypoplastic or absent. As mentioned above, identifying the presence or absence of the pituitary stalk is important as it correlates with the degree/ type of hormonal abnormality.