1	Congenital Abnormalities of the Sellar and Parasellar Regions Maria Vittoria Spampinato, John Grimme, Daniel L.A. Camacho, and Mauricio Castillo Section of Neuroradiology Department of Radiology University of North Carolina at Chapel Hill
2	Overview of this Presentation I. Embryology of the pituitary gland II. Congenital disorders related to development of the hypothalamo-pituitary axis III. Congenital disorders related to development of the adenohypophysis IV. Disturbances of separation of surface ectoderm and neurectoderm V. Miscellaneous VI. References
3	Embryology The pituitary gland consists of two embryological and functionally distinct divisions: Adenohypophysis (pars anterior, pars intermedia and pars tuberalis) Neurohypophysis (median eminence, infundibular stem and pars posterior)
4	Embryology Development of the pituitary gland begins in the 4^th week of life with inductive signals from the diencephalon initiating the formation of Rathke's pouch Rathke’s pouch has been considered as a diverticulum of the epithelial lining of the stomodeum, but recent evidence indicates it is a derivative of neural ectoderm from the anterior neural ridge
5	Embryology By the 8^th week of life, the primitive adenohypophysis separates from the oral cavity and primitive pituitary cells undergo rapid proliferation with differentiation into specialized hormone lines Adenohypophysis consists of: pars anterior or distalis, pars intermedia (rudimentary in humans) and pars tuberalis (along the stalk)
6	Embryology Neurohypophysis originates from a neuroectodermal evagination of tissue in the diencephalic floor which grows to the stomodeal roof. An extension of the 3^rd ventricle (the infundibular recess), persists in the neuroectodermal diverticulum of the forebrain Neurohypophysis is divided into median eminence, infundibular stem and pars posterior
7	Embryology
8	Figure 1B. Pituitary at 11 weeks of life. The gland is formed and a cleft persists between pars intermedia and pars anterior. The craniopharyngeal canal closes and occasionally the adenohypophysis remains in the nasopharynx (used with permission).
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10	Embryology Regulation of pituitary embryogenesis involves a cascade of genes expressed during the 4^th week of life in the diencephalon initiating formation of Rathke‘s pouch and later a combined expression of multiple genes throughout the stomodeal epithelium required for morphogenesis of the pouch and proliferation and differentiation of hormone specific cells
11	Congenital Abnormalities Development of the Hypothalamo-Pituitary Axis
12	"Pituitary hypoplasia is a congenital..." Pituitary hypoplasia is a congenital disorder involving the adenohypophysis, neurohypophysis and often the stalk Patients with pituitary hypoplasia survive with hormonal replacement but pituitary aplasia is incompatible with life Pituitary dwarfism due to deficiency of growth hormone is a common clinical presentation
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14	Pituitary and Hypothalamic Hypoplasia
15	Ectopic Neurohypophysis It is characterized by a “bright spot” along median eminence of hypothalamus or along stalk which may be tiny or absent Adenohypophysis and sella may be small Frequently associated with growth hormone deficiency (pituitary dwarfism) Associated adenohypophysis dysfunction may be related to absent infundibulum Associated midline CNS abnormalities: (septo-optic dysplasia, lobar holoprosencephaly, olfactory bulb anomalies)
16	Ectopic Neurohypophysis
17	Ectopic Neurohypophysis
18	Ectopic Neurohypophysis with Probable Partial Intrasellar Neurohypophysis
19	Ectopic Neurohypophysis with Thin Stalk
20	Duplicated Pituitary Gland Rare congenital disorder due to duplication of primitive stomodeal structures Two sellae, lateral stalks and glands are present Mammillary bodies are fused with tuber cinereum, thickening of 3^rd ventricle floor (hamartoma?) Basilar artery shows lack of longitudinal fusion Anterior 3rd ventricle may be duplicated Possible association with CN I and II hypoplasia Pituitary-related symptoms are rare Associations: craniofacial clefting, oral midline tumors, dysgenesis of corpus callosum, Dandy-Walker spectrum
21	Duplicated Pituitary Gland
22	Tuber Cinereum Hamartoma It is a congenital heterotopia of gray matter in region of tuber cinereum Round non-enhancing pedunculated or sessile mass, contiguous with tuber cinereum; isointense to gray matter on T1 and slightly T2 bright Precocious puberty due to LHRH and/or gelastic seizures Common associations: congenital facial/cerebral midline abnormalities, visceral anomalies, digital malformations Differential diagnosis: hypothalamic astrocytoma, hystiocytosis, germ cell tumor
23	Tuber Cinereum Hamartoma
24	Tuber Cinereum Hamartoma
25	Optic Infundibular Hypoplasia Disorder of midline prosencephalic development (6^th weeks of life) Overlaps with septo-optic dysplasia but septum pellucidum is present Optic chiasm/optic nerves are hypoplastic Pituitary hypoplasia, thin stalk, ectopic neurohypophysis may be present
26	Optic Infundibular Hypoplasia
27	Stalk Fenestration or Dilated Infundibular Recess of 3^rd Ventricle?
28	Congenital Disorders Development of the Adenohypophysis
29	Persistent Craniopharyngeal Canal
30	Persistent Craniopharyngeal Canal
31	Rathke’s Cleft Cyst Non-neoplastic cyst arising from remnants of squamous epithelium of Rathke’s cleft Non-enhancing non-calcified intra or supra-suprasellar cyst Variable cyst content: mucous (T1 bright) serous (T1 dark) and possible blood products (T2 dark)
32	Rathke’s Cleft Cyst
33	Rathke’s Cleft Cyst
34	Rathke’s Cleft Cyst
35	Craniopharyngioma Benign dysontogenetic epithelial tumor arising from cell remnants of Rathke’s pouch Complex mass, with inhomogeneous enhancement of solid components Calcifications: very common T1 signal varies with cyst contents Bimodal age distribution (5-15 y; > 50)
36	Craniopharyngioma
37	Craniopharyngioma
38	Pars Intermedia Cyst These cysts arise in the pars intermedia of the adenohypophysis which is rudimentary in humans They are usually less than 3 mm in diameter They are located between the pars anterior and pars posterior
39	Pars Intermedia Cyst
40	Abnormal Separation of Ectoderm and Neuroectoderm
41	Transsphenoidal Encephalocele Is an “occult” encephalocele characterized by a bone defect in ethmoid or sphenoid bone Usually diagnosed later than other forms of encephaloceles Hypothalamus, pituitary gland, 3^rd ventricle, optic nerves and chiasm may be located in the encephalocele sac Typical clinical presentation: nasal obstruction, difficulty feeding and failure to thrive
42	Transsphenoidal Encephalocele
43	Miscellaneous
44	Dermoid Intracranial dermoids are ectodermal inclusion cysts that originate from midline inclusion of surface ectoderm during the 3^rd-5^th weeks of life at the time of closure of the neural tube Common intracranial locations: frontonasal, sellar and parasellar regions, posterior fossa and ventricles Dermoids are T1 bright due to presence of lipids and cholesterols and may rupture with spreading of fat droplets along the CSF containing spaces resulting in aseptic meningitis
45	Dermoid
46	Teratoma Teratomas are composed of tissues from the three embryonic germ layers The majority of teratomas are supratentorial in the region of the optic chiasm and in the pineal gland They are midline tumors containing fat, soft tissue and calcifications Classified as mature, immature and malignant Occasionally they present in newborns as holocranial tumors
47	Teratoma
48	Newborn Pituitary Gland
49	References