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KEY FACTS

Terminology
- Congenital anomalies of pituitary stalk → potential hypothalamic/pituitary axis malfunction
Imaging
- Posterior pituitary ectopia (PPE) - No (or tiny) pituitary stalk, ectopic posterior pituitary (EPP) on midline sagittal T1WI MR - Look for associated anomalies: Heterotopia, optic nerve hypoplasia, corpus callosum anomalies
- Duplicated pituitary gland/stalk (DP) - 2 pituitary stalks on coronal view, thick tuber cinereum on midline sagittal view
Top Differential Diagnoses
- PPE - Surgical or traumatic stalk transection - Central diabetes insipidus - Hypothalamic lipoma (in tuber cinereum)
- DP - Dilated infundibular recess of 3rd ventricle ("pseudoduplication") - Tuber cinereum hamartoma
Pathology
- PPE: Genetic mutation → defective neuronal migration during embryogenesis
- DP: Genetic mutation unknown; may constitute polytopic field defect due to splitting of notochord
Clinical Issues
- PPE: Short stature
- DP: Unsuspected finding on craniofacial imaging for other indications
Diagnostic Checklist
- PPE: Assess optic and olfactory nerves, frontal cortex
- DP: Oral tumors compromise airway patency

TERMINOLOGY

Synonyms
- Ectopic pituitary bright spot
Definitions
- Congenital anomalies of pituitary stalk → potential hypothalamic/pituitary axis malfunction

IMAGING

General Features

Best diagnostic clue

- Posterior pituitary ectopia (PPE): No (or tiny) pituitary stalk, ectopic posterior pituitary (EPP) on midline sagittal T1WI MR
        - Partial pituitary ectopia also reported
- Duplicated pituitary gland/stalk (DP): 2 pituitary stalks on coronal view, thick tuber cinereum on midline sagittal view
        - Tuberomammillary fusion: Tuber cinereum/mammillary bodies fused into single mass
- Pituitary hypoplasia: Small sella turcica and adenohypophysis

Location

- PPE: EPP located along median eminence of tuber cinereum or truncated pituitary stalk
- DP: Paired lateral stalks, pituitary glands, bony fossae

Size

- PPE: Anterior pituitary (adenohypophysis) is small
- DP: Each pituitary gland is normal in size

Morphology

- PPE: Small adenohypophysis and osseous sella
- DP: Each pituitary gland and osseous sella is normal in morphology but laterally located

Radiographic Findings

Radiography

- PPE: Small sella turcica on lateral view
- DP: Craniofacial/craniocervical anomalies common; may observe 2 fossae on AP view

CT Findings

NECT

- PPE: Narrow pituitary fossa and skull base structures and clivus, ± persistent sphenopharyngeal foramen
- DP: 2 widely separated pituitary fossae, ± midline basisphenoid cleft or frontonasal dysplasia

CTA

- PPE: Medial deviation of juxtasellar/supraclinoid carotid arteries ("kissing" carotids)
- DP: Duplicated basilar artery (BA), ± widely separated juxtasellar/supraclinoid carotid arteries

MR Findings

T1WI

- PPE: Absent, truncated, or thread-like pituitary stalk; small adenohypophysis
        - EPP located along truncated stalk or median eminence of tuber cinereum
                  - Usually ↑ signal on T1WI (phospholipids/secretory granules)
                  - Posterior pituitary may "dim" as patient outgrows available hormone levels
        - Chiari 1 (20%), ± olfactory hypoplasia, frontal lobe dysgenesis/migration anomalies
        - ± absent septum pellucidum, ocular dysgenesis, hypoplastic optic nerves/chiasm
- DP: Mass-like thickening of tuber cinereum on sagittal view portends duplicated pituitary axis
        - Mammillary bodies fused with tuber cinereum into thickened 3rd ventricle floor
        - 2 lateralized but otherwise normal pituitary glands/stalks
        - Brain anomalies: Callosal dysgenesis, duplicated anterior 3rd ventricle, cleft brainstem, Dandy-Walker malformation
        - Cranial nerve anomalies: Olfactory nerve and optic nerve hypoplasia
        - Oral tumors: Epignathus (giant teratoma) or dermoid (mixed signal), lipoma (↑ T1WI)

T2WI

- PPE: Variable signal of posterior pituitary
- DP: Normal signal of glands, stalk, tuberomammillary fusion mass

T1WI C+

- Both: Stalks and remnants enhance (absent blood-brain barrier)
- PPE: Hyperintensity absent if multiple endocrine anomalies/diabetes insipidus; contrast enhancement helps find neurohypophysis

MRA

- PPE: Supraclinoid carotid arteries medially deviated, "kiss" in midline; rare absent carotid artery/canal
- DP: Fenestration (common) or total duplication (rare) of BA; widely separated juxtasellar carotid arteries

MRV

- Used to characterize torcular and straight sinus anomalies if midline posterior fossa anomaly identified

Angiographic Findings
- Conventional - PPE: Variable deviation "kissing" carotids (37%) - DP: Split/duplicated BA, ± lateral deviation carotids

Imaging Recommendations

Best imaging tool
```
- Multiplanar T1WI MR
```

Protocol advice

- Both: Sagittal and coronal T1WI ± T2WI of hypothalamic/pituitary axis
- PPE: Assess olfactory nerves, anterior frontal lobes with coronal T2WI
        - 3D T1WI SPGR can identify small posterior pituitaries, occult on conventional 2D sagittal T1WI
- DP: 3D CT of skull base and face in selected patients

DIFFERENTIAL DIAGNOSIS

Posterior Pituitary Ectopia
- Central diabetes insipidus - Hyperintensity of posterior pituitary lobe is absent but normal location of stalk and gland
- Surgical or traumatic stalk transection - Permits build-up of neurosecretory granules along stump
- Hypothalamic lipoma (located at tuber cinereum) - Posterior pituitary is not suppressed by fat saturation; lipoma is suppressed
Duplicated Pituitary Gland/Stalk
- Dilated infundibular recess of 3rd ventricle ("pseudoduplication") - Simulates duplicated stalk but only 1 gland and 1 pituitary fossa
- Tuber cinereum hamartoma - Round mass of 3rd ventricle floor but 1 midline pituitary stalk/gland

PATHOLOGY

General Features

Etiology

- PPE: Genetic mutation → defective neuronal migration during embryogenesis
        - Adenohypophysis (anterior pituitary) grows up from stomodeal ectoderm (Rathke pouch)
                  - Hypothalamic-releasing hormones reach adenohypophysis via infundibular portal system
                  - Anterior pituitary dysfunction thought to be related to absent infundibulum
        - Neurohypophysis (posterior pituitary) grows down from diencephalic neuroectoderm, remains attached by stalk
                  - Antidiuretic hormone and oxytocin transported to neurohypophysis via neurosecretory cells along infundibulum
- DP: Congenital anomaly, presumed genetic duplication of stomodeal origin structures 2° to aberrant ventral induction
        - Theory: Duplication prechordal plate and tip of rostral notochord leads to duplicated pituitary primordium

Genetics

- PPE: Mutations in genes encoding developmental transcription factors allow maldevelopment
        - *HESX1* (homeobox gene), *POU1F1* (PIT1), *PITX2*, *LHX3*, *LHX4*, *PROP1*, *SF1*, and *TBX19* (TPIT)
- DP: Gene mutation unknown; may constitute polytopic field defect due to splitting of notochord

Associated abnormalities

- DP
        - Midline tumors in oral, nasopharyngeal, palate
                  - Epignathus, hamartomas, teratomas, dermoids, lipomas
        - Spinal anomalies include segmentation/fusion anomalies, schisms, hydromyelia, enteric cysts
        - Rib and cardiac anomalies, Pierre-Robin anomaly
- **Both**: Common midline CNS anomalies
        - PPE
                  - ± anomalies of structures formed at same time (anterior pituitary lobe, forebrain, eyes, olfactory bulbs)
                  - ± lobar holoprosencephaly, septo-optic dysplasia, Joubert syndrome
        - DP
                  - Callosal dysgenesis, Dandy-Walker spectrum, frontonasal dysplasia
                  - Craniofacial clefting and duplication anomalies: Frontonasal dysplasia; clefts/duplication of skull base, face, mandible, nose, palate
- Pituitary hypoplasia associated with Kallmann syndrome

Gross Pathologic & Surgical Features
- PPE: Hypoplastic anterior lobe, stalk truncation or aplasia - Sella may be covered over with dura
- DP: Tuberomammillary fusion, 2 normal glands/stalks
Microscopic Features
- PPE: Ectopic pituitary cells in stalk or sphenoid bone
- DP: Normal (but duplicated) pituitary glands, tuberomammillary fusion, incompletely migrated hypothalamic nuclear cells

CLINICAL ISSUES

Presentation

Most common signs/symptoms

- PPE: Short stature
- DP: Unsuspected finding on craniofacial imaging for other indications

Other signs/symptoms

- PPE: Multiple pituitary hormone deficiencies common
- DP: Rarely symptomatic from pituitary causes

Clinical profile

- PPE: Short stature (growth hormone deficiency), ± multiple endocrine deficiencies
        - Peak growth hormone levels < 3 g/L more likely to have abnormal MR
        - ± anosmia, poor vision, seizures (cortical malformations)
        - Neonatal hypoglycemia or jaundice, micropenis, single central incisor
- DP: ± facial midline anomalies, oral or nasal mass (hamartoma or teratoma)
        - Face: ± hypertelorism or frontonasal dysplasia
        - Craniocervical segmentation and fusion anomalies
        - Airway or oral obstruction from pharyngeal tumor

Demographics

Age

- PPE: Early growth failure apparent in childhood
- DP: Usually discovered in early infancy during imaging for complicated facial anomalies

Sex
```
- PPE: M > F
- DP: M < F
```
Ethnicity
```
- None identified in either diagnosis
```

Epidemiology

- PPE: Prevalence 1:4,000 to 1:20,000 births
- DP: Extremely rare (reported in 20+ cases)

Natural History & Prognosis
- PPE: Stable if no pituitary/hypothalamic crises; growth may be normal for a while - Severity and number of hormone deficiencies predicted by degree of stalk and gland hypoplasia
- DP: Usually significant intracranial, upper airway, or craniocervical malformations (some lethal) - Clinical outcome unrelated to pituitary function
Treatment
- Assess/treat endocrine malfunction

DIAGNOSTIC CHECKLIST

Consider
- PPE: Assess optic and olfactory nerves, frontal cortex
- DP: Oral tumors compromise airway patency
Image Interpretation Pearls
- PPE/DP: Can miss findings/diagnosis if thick sections (MR) are used or osseous structures (bone CT) not evaluated

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References

Selected References

Images

Selected Images

Sagittal graphic shows ectopia of the posterior pituitary gland located at the distal end of a truncated pituitary stalk along the median eminence of the hypothalamus. The sella turcica and adenohypophysis are both small.

Sagittal T1 MR shows an ectopic posterior pituitary gland in a 17-year-old girl with short stature. The T1-hyperintense posterior gland is at the median eminence instead of its normal position. The pituitary infundibulum is absent and the anterior pituitary gland is small.

Coronal T1 MR depicts the ectopic posterior pituitary gland location at the median eminence of the hypothalamus. A pituitary stalk is not visualized below the ectopic posterior pituitary. The septum pellucidum is present, and the optic tracts are of normal size.

Sagittal T2 MR in a patient with complete absence of the posterior pituitary bright spot shows a small sella turcica and pituitary gland . The optic apparatus is also hypoplastic. A clearly defined pituitary stalk is present.

Sagittal T1 MR shows a small pituitary gland and absent pituitary stalk. The hyperintense ectopic posterior pituitary gland is located at the median eminence. The corpus callosum is also dysmorphic with characteristic small splenium .

Coronal T2 MR in the same patient demonstrates associated left periventricular nodular gray matter heterotopia and dysplastic inferior temporal lobe gray matter. Right choroid fissure cyst is probably unrelated.

Sagittal T1 MR demonstrates a bright ectopic posterior pituitary gland in a patient with septo-optic dysplasia. Note the small optic chiasm and the low location of the fornices .

Sagittal T1 MR in a patient with duplicated pituitary glands shows a thickened floor of sella and fusion of the tuber cinereum and mammillary bodies (tuberomammillary fusion) . Note the absence of a midline sella turcica and pituitary infundibulum.

Coronal T2 MR in a newborn with midline skull base clefting reveals 2 pituitary stalks . The normal-sized pituitary stalks project below the optic chiasm toward duplicated pituitary glands.

Coronal T1 MR demonstrates 2 normal-sized pituitary glands laterally displaced within the abnormal skull base. The glands are uniformly hyperintense due to maternal hormonal influences. The pituitary gland is normally diffusely hyperintense on T1 MR in newborns.

Additional Images

Sagittal T1WI MR reveals a small anterior pituitary gland and ectopic posterior pituitary bright spot located along tuber cinereum. Pituitary stalk is absent in this 2 year old with growth failure.

Coronal MRA in a patient with ectopic posterior pituitary bright spot shows marked medial deviation of the juxtasellar/supraclinoid internal carotid arteries. Note right deviated internal carotid artery and dominant left anterior cerebral artery (ACA).

Coronal MRA in an infant with pituitary duplication demonstrates partial duplication of the upper basilar artery. Note that each superior cerebellar artery arises from its "own" basilar artery.

Coronal T1WI MR depicts the ectopic posterior pituitary gland location at the median eminence . A pituitary stalk is not visualized below the ectopic posterior pituitary. The septum pellucidum is present, and the optic tracts are of normal size.

Axial T1WI C+ MR confirms the ectopic position of the bright posterior pituitary gland at the median eminence in the expected location of the infundibular stalk base.

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KEY FACTS

Terminology

Imaging

Top Differential Diagnoses

Pathology

Clinical Issues

Diagnostic Checklist

TERMINOLOGY

Synonyms

Definitions

IMAGING

General Features

Best diagnostic clue

Location

Size

Morphology

Radiographic Findings

Radiography

CT Findings

NECT

CTA

MR Findings

T1WI

T2WI

T1WI C+

MRA

MRV

Angiographic Findings

Imaging Recommendations

Best imaging tool

Protocol advice

DIFFERENTIAL DIAGNOSIS

Duplicated Pituitary Gland/Stalk

PATHOLOGY

General Features

Etiology

Genetics

Associated abnormalities

Gross Pathologic & Surgical Features

Microscopic Features

CLINICAL ISSUES

Presentation

Most common signs/symptoms

Other signs/symptoms

Clinical profile

Demographics

Age

Sex

Ethnicity

Epidemiology

Natural History & Prognosis

Treatment

DIAGNOSTIC CHECKLIST

Consider

Image Interpretation Pearls

References

Selected References

Images

Selected Images

Additional Images

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