Imaging of Sellar and Parasellar Diseases

Dr K Rodgers

Radiology Dept

Kingston Public Hospital

Overview

• Review of Anatomy

• Physiology

• Clinical Features

• Imaging Modalities

• Differential Diagnosis

Review of Anatomy

Embryology• Derived from two different parts

– Anterior lobe (Adenohypophysis)- an invagination of the oral ectoderm (Rathke’s Pouch)

– Posterior lobe (Neurohypophysis) - protrusion of the neural ectoderm of the diencephalon (Infundibulum)

• Between the anterior and posterior lobes lies an intermediate lobe – Pars intermedia (a potential site for small

non-functional Rathke’s cysts )

Review of Anatomy

• Pituitary gland lies within sella turcica (cup-shaped depression in sphenoid bone)– Superiorly – Suprasellar cistern with optic chiasm– Inferiorly and anteriorly – Sphenoid air sinus– Laterally – Cavernous sinus with Internal carotid

arteries and Cranial nerves 3, 4, 6, 5 (1st and 2nd divisions)

• Connects to hypothalamus via pituitary stalk– Hypothalamus makes up floor of anterior part of

3rd ventricle

Review of Anatomy A Anterior pituitary

P Posterior pituitary

C Optic chiasm

S Sphenoid air sinus

M Mamillary body

B Brainstem

CL Clivus

→ Stalk

Sagittal T1

Coronal T1

Review of Anatomy• Characteristics

– Birth • Globular in shape• High signal on T1 weighted images

– Age 6 weeks• High signal has diminished in anterior pituitary tissue (now

similar signal to brain tissue)• Posterior pituitary tissue - retains a bright signal on T1

weighted sequences (“Posterior pituitary bright spot” - due to the high neurophysin content)

• Size– 3mm - 8mm in height (larger in females than males)

• increases during adolescence (normal physiological hypertrophy)

• slight increase in size seen during the sixth decade in females

• Pregnancy - maximal height post partum of 10mm

Physiology• Anterior pituitary

•Gonadotrophins (FSH & LH)•Prolactin•Growth hormone•Adrenocorticotrophin (ACTH)•Thyroid stimulating hormone

•Posterior pituitary•Oxytocin•ADH

Clinical features

• Based on location, size and secretory capability• Functional tumors

– Symptoms due to excess hormone release• Prolactin (Prolactinoma), ACTH (Cushing’s Disease), TSH

(Thyrotoxicosis), GH (Acromegaly)– Usually microadenomas (<10 mm) – detected earlier clinically

• Except Acromegaly which may be detected late• Non-functional tumors

– Symptoms due to compression• Visual loss (Bitemporal), Double vision, facial numbness

– Usually macroadenomas by time of detection– Gonadotrophins (FSH, LH)

Imaging modalities - MRI

• MRI is modality of choice to image pituitary gland. Standard protocol:– Precontrast T1 weighted thin slices (2mm or 3mm) through the sella

in coronal and sagittal planes– Gadolinium contrast

• Pituitary gland, stalk and cavernous sinuses – enhance• Optic chiasm and hypothalamus – no enhancement if the blood

brain barrier is intact– Repeat coronal and sagittal T1 sequences– T2 not standard but may be useful to detect cystic changes and

haemorrhage

Imaging Modalities - CT

• CT useful in patients – With contraindications to MRI – To detect calcification in or around the sella

• Ideally – MDCT• Single-channel axial and helical CT

– Direct coronal plane with maximal extension of neck in supine or prone position

– Or axial with thin 1 mm axial contiguous sections• 120kV, 200mA, 2-second scanning time• Soft tissue algorithm• Reformatting in coronal and sagittal planes

Differential Diagnosis

• Type– Adenomas

• Macro and Micro

– Rathke’s Cleft cyst– Meningioma– Craniopharyngioma– Hypothalamic/ Optic

chiasm gliomas– Germinoma– Granular cell tumor– Langerhan Cell

Histiocytosis

– Empty Sella – Arachnoid cyst– Congenital Pituitary Abn

• Anatomical• Other

– Lipoma– Hamartoma

– Skull Base Tumors• Chordoma• Chondrosarcoma

– Metastases

Differential Diagnosis

• Location

Pituitary Adenomas

• Most common mass lesion of the sella and parasellar

region

• Slow-growing benign neoplasms of anterior pituitary

• Micro (<10mm), Macro (>10mm)

• Functional versus Non-functional

Pituitary Macroadenoma

• Compression symptoms/ Invasion– Superiorly - into suprasellar cistern– Lateral growth

• Deformity of the cavernous sinus• Invasion into cavernous sinus

– Inferiorly into the sphenoid producing remodelling of the bone

• “Waisting” - pass through the diaphragma sellae

Pituitary Macroadenoma

• MR signal – Homogeneous or heterogeneous– Cystic change and focal areas of haemorrhage

• Pituitary apoplexy - significant hemorrhage w/ necrosis

–macroadenoma with areas of high T1 signal representing the haemorrhage

Unenhanced sagittal and coronal

“Waisting”

Haemorrhage

Pituitary Microadenoma

• Confined within the sella• Area of lower signal on T1 weighted sequences than the

normal pituitary tissue• Local remodelling of the floor of the sella and the dorsum• IV Gad

– Enhance less than the normal anterior pituitary tissue – Dynamic acquisition in first minute

• Less vascular on the initial arterial phase• Similar vascularity to the normal gland in the next few

minutes.• Post-op

– 3 to 4 months before true assessment volume of residual pituitary tissue

Unenhanced – depression of floor of sella

Hypointense area post contrast

Post contrast

Rathke’s Cleft Cyst

• Remnants of squamous epithelium from Rathke’s cleft• Hyperintense on the T1 weighted sequence• If of significant size - hard to distinguish from a cystic

craniopharyngioma– Wall of a Rathke’s cyst shows no more than minimal

enhancement– No solid enhancing areas– No calcification

Large Rathke’s cyst

Meningioma

• Dural slow growing neoplasms– Suprasellar meningiomas

• Soft tissue mass atop the superior surface of the pituitary

• Compressing or involving the optic chiasm and nerves– From the cavernous sinus

• Lateral to normal pituitary tissue• Encase the cavernous carotid artery

– Constriction » Differentiate from pituitary tumours - do not

typically cause vascular constriction

Meeningioma

• Dural “tail” of enhancement along the planum

sphenoidale

• MR features - similar to brain parenchyma and

pituitary gland with prominent homogeneous

enhancement after contrast

• Hyperostosis - most typically the anterior clinoid

process

Craniopharyngioma

• Rare epithelial tumours - remnants of the craniopharyngeal duct• Commonest lesion of hypothalamic/pituitary region in children• Histological subtype

– Adamantinomatous most common in children• Cystic , solid components and calcification

– Cyst fluid –high signal T1 unenhanced» High cholesterol content and protein

• Adherent to surrounding tissue– Papillary subtype in adulthood

• Solid lesions or mixed solid and cystic morphology• Do not typically calcify and are less locally infiltrative

Patchy areas of high signal before contrast which represent the cystic components with a high protein/ lipid content.

Hypothalamic/ Optic chiasm gliomas• Suprasellar mass lesions in children commonly• Optic chiasm AND hypothalamus usually involved

simultaneously• Associated with Neurofibromatosis type I

– Optic nerve involvement– Significant cystic component

• Well-defined suprasellar mass lesions with enhancement and reactive signal change along the optic radiation– No calcification

Germinoma

• Rare intracranial germ cell tumours• Suprasellar or pineal regions • MR features

– Homogeneous, solidly enhancing mass in the hypothalamic region with involvement of the upper aspect of the pituitary stalk

• Detection of tumour markers– human chorionic gonadotrophin (HCG) or alpha fetoprotein (AlphaFP)

in the serum/CSF to confirm the diagnosis– Absence does not exclude diagnosis – biopsy

• Very sensitive to radiation• Disseminate through the CSF spaces - enhancement around ventricular

margins

Granular Cell Tumors

• Rare lesions in the suprasellar region• Arise from the neurohypophysis and/or the pituitary stalk• AKA - pituicytomas, infundibulomas or choristomas

• Well-defined suprasellar mass related to the pituitary stalk with homogenous enhancement

• Asymptomatic/ visual disturbance or headache• Benign and slow growing• Low recurrence rate after surgery

Langerhan Cell Histiocytosis

• Proliferative disorder of the Langerhans cell of the dendritic cell line

• Most frequently skeletal involvement• Intracranial involvement commonly hypothalamo- pituitary

axis• MR features

– Thickening of the pituitary stalk with enhancement– Absent posterior pituitary bright spot

Hypophysitis

• Idiopathic inflammatory lesion of the pituitary gland– Lymphocytic hypophysitis, Granulomatous hypophysitis

• Enlargement of gland - appearance of a sellar mass lesion with suprasellar involvement of the stalk

• Heterogeneous post contrast with chiasmal distortion of the chiasm

• Lymphocytic type – Classically females at end of pregnancy or the post-partum period with endocrine dysfunction

– Xanthomatous hypophysitis• Least common • Distinctly cystic appearance• Intrasellar cyst without suprasellar extension or involvement of the

stalk

Empty Sella

• Only CSF with no visible pituitary tissue• Visible pituitary stalk extends into the floor of the sella• Due to

– Previously documented pituitary/hypothalamic pathology or treatment

• Surgery, radiotherapy, hypophysitis, Sheehan’s syndrome or pituitary apoplexy)

– Incidental (“Primary empty sella”)• Women > Men• Intracranial hypertension, obesity, visual disturbance and

spontaneous CSF leaks ± Endocrine problems

Prolapsed optic chiasm

Arachnoid Cysts

• Benign, congenital CSF-containing cysts arising within the arachnoid membrane

• Suprasellar region• MR features

– Same signal as CSF on all MR imaging sequences– No enhancement after contrast– No calcification

Marked elevation of the hypothalamus and stretching the pituitary stalk

Elevation of the right side of the chiasm by the cyst. No cyst wall is evident and the pituitary tissue itself is normal.

Congenital Pituitary Abnormalities• Congenital hypopituitarism

– May be due to anatomic abnormalities• Ectopic

– High signal area in median eminence– Absent pituitary stalk– Hypoplasia of anterior pituitary tissue– Abnormalities of midline structures (septum pellucidum,

corpus callosum etc)

Small pituitary fossa containing a reduced volume of anterior pituitary tissue. The stalk cannot be seen and the posterior pituitary bright spot (arrow) is lying in an ectopic location within the hypothalamus.

Incidentals

• Lipoma - Suprasellar cistern– MR

• High T1 signal mass adjacent to normal hypothalamic and pituitary structures

• FatSat - obliterate the signal from the mass• Hamartoma - Tuber cinereum of the hypothalamus

– Composed of well differentiated neurones and glial cells– Associated with central precocious puberty, gelastic (laughing) seizures

and sometimes developmental delay– MR

• Pedunculated rounded mass hanging from the hypothalamus• Isointense to grey matter of the brain• No enhancement

– Surgical resection if refractory seizures

High signal mass lying just below the hypothalamus and behind the pituitary stalk in the suprasellar cistern. The pituitary tissue and stalk are normal.

Lipoma

Non-enhancing mass visible arising from the undersurface of the hypothalamus and lying behind the pituitary stalk

Skull Base Tumors

• Chordoma – Remnants of the primitive notochord– Centrally located, expansile masses arising from the clivus– High signal on T2 weighted images– Bony destruction on CT

• Chondrosarcomas– Malignant mesenchymal tumours– Similar appearance - but just lateral to the clivus at the site of the

petroclival synchondrosis• Not possible to distinguish both radiologically

Bony destruction of clivus. Preservation of sella.

Axial T2 Axial T1

Typical bubbly high T2 signal with involvement of the right side of the pituitary fossa , the Rt cavernous sinus and extends into the Rt middle cranial fossa.

Metastases

• Uncommon - diffuse malignancy• Breast and lung• Diffuse enlargement of the gland with thickening of the stalk in a patient

with known malignancy

Other

• Carotid Arteries

– Aneurysm

– Ectasia

• Cavernous Sinus

– Schwannoma

– Inflammation

– Car-Cav Fistula

Tumour Typical featuresPituitary macroadenoma Enlarged sella turcica, strong enhancement, sometimes

haemorrhage

Rathke's cleft cyst T1-hyperintense on MRI, smooth peripheral enhancement

Meningioma

Broad dural base, enhancement along planum sphenoidale

Hyperostosis, ‘blistering’ of sphenoid sinus

Crangiopharyngioma Calcification, cysts, nodular enhancement

Optic glioma Thickening of chiasm, spread along optic pathways

Germ cell tumours Located in midline, intense enhancement; can be synchronous with pineal germinomas

Tumor Typical Features

Tuber cinerum Grey matter isointense on T1 weighting and T2 hamartoma hyperintense

Chordoma Bone destruction on CT, heterogeneous signal and enhancement on MRI

Chondrosarcoma Bone destruction and calcification on CT, T2 hyperintense on MRI

THANK YOU

References• The Radiology Assistant – Sella Turcica and Parasellar region

– http://www.radiologyassistant.nl/en/485d7745cc720• Pituitary Adenoma Imaging

– http://emedicine.medscape.com/article/343207-overview• Radiology of the Pituitary

– http://www.endotext.org/neuroendo/neuroendo4/neuroendoframe4.htm

• Imaging Pituitary Gland Tumors– http://eradiology.bidmc.harvard.edu/LearningLab/central/

Varshney.pdf