Clinical anatomy of the pituitary and cavernous sinus Flashcards
what is the cavernous sinus
Paired venous cavities that sit on either side of the sphenoid bone, extending from the most posterior aspect of the orbit to the petrous part of the temporal bone.
drains to Superior and inferior petrosal sinuses
what is a carotid cavernous fistula
carotid-cavernous fistula (CCF) is the result of an abnormal vascular connection between the internal carotid artery (ICA) or external carotid artery (ECA) and the venous channels of the cavernous sinus.
cavernous sinus thrombosis symptoms
a sharp and severe headache, particularly around the eye.
swelling and bulging of the eye(s) and the surrounding tissues.
eye pain that’s often severe.
double vision.
a high temperature
what is the relationship between the pituitary gland and the cavernous sinus
The pituitary gland lies between the two paired cavernous sinuses. An abnormally growing adenoma will expand in the direction of least resistance and eventually compress the cavernous sinus
what passes through the cavernous sinus so are first affected
The internal carotid artery and the abducens nerve pass through the cavernous sinus.
Adenohypophysis (Anterior lobe).
what cells types
Somatotrophs
secrete Growth hormone (GH), also known as human growth hormone (hGH).
Thyrotrophs
secrete Thyroid-stimulating hormone (TSH), also known as thyrotropin.
Gonadotrophs secrete two Gonadotropins: Follicle-stimulating hormone (FSH). Luteinizing hormone (LH).
Lactotrophs
secrete Prolactin.
Corticotrophs adrenocorticotropic hormone (ACTH), also known as corticotropin. some corticoprophs, remnant within the pars intermedia also secrete melanocyte-stimulating hormone (MSH).
What are the hormones released by the posterior lobe (Neurohypophysis) of the Pituitary gland?
Oxytocin (OT).
plays an important role in reproduction, initiating contractions before birth as well as milk release.
Antidiuretic hormone (ADH). increases the amount of solute-free water reabsorbed from the tubules of the kidney. constricts arterioles, which increases peripheral vascular resistance and raises arterial blood pressure.
Describe the attachments of the dura mater around the body of the sphenoid bone.
Diaphragma sella
Tentorium cerebelli
Describe the embryological origin and functional anatomy of the pituitary gland.
Derived from two embryonic sources:
Non-neural (Glandular) part
Anterior pituitary - forms from rathke’s pouch - ectodermal out pocketing of roof of oral cavity - foregut (stemoddeum)
Neural part- from infundibulum of the diencephalon
Posterior pituitary
Adenohypophysis made of
Pars distalis - largest part, arises from the anterior wall of Rathke’s Pouch
Pars tuberalis - surrounds the anterior aspect of the infundibular stalk.
Pars intermedia - thin layer of epithelial cells between pars distalis and neurohypophysis, arises from the posterior wall of Rathke pouch
A system of blood vessels connecting the hypothalamus with the anterior pituitary.
Transports and exchanges hormones between these structures via the pituitary stalk
Peptides released from median eminence of hypothalamus include:
Gonadotropin-releasing hormone (GnRH): regulates release of FSH and LH mediating reproductive activity and development
Corticotropin-releasing hormone (CRH): regulates the release ACTH – mediates stress response
Growth hormone-releasing hormone (GHRH): regulates the release of GH – mediates cell growth, metabolism, and reproduction
Thyrotropin-releasing hormone (TRH): regulates the release of TSH - mediates various responses in the thyroid gland, and thus metabolism
released from where
pituitary portal venous system
Pituitary tumours (adenomas) are the most common pituitary disease and may be Functioning (secrete hormones) Non-functioning
classified how
They may be classified on the basis of their size
<1cm = microadenomas, will generally only present clinically if functioning
>1cm = macroadenomas, may present with hormonal changes or mass effect
Non-functioning macroadenomas may cause hormonal imbalance due to compression of pituitary stalk (hyperprolactinaemia) other functional areas of the pituitary (hypopituitarism) .
what can pituitary tumours compress - macros
Compression of the optic chiasm
Bi-temporal hemianopia
Compression of the cavernous sinus
cranial nerve palsies.
Compression of the portal venous system within the pituitary stalk
Dopamine transported from hypothalamus inhibits prolactin secretion
Compression of the stalk therefore results in hyperprolactinaemia
This may manifest as galactorrhoea, infertility, and amenorrhoea
Compresssion of the diaphragma sella
Headache
Compression of the ventricular system leading to hydrocephalus (rare)
implications of pituitary Gladn hormonal problems with its secretions
Presentation of functioning tumours depends on hormone secreted:
Growth hormone (somatotropin) - acromegaly
Thyroid stimulating hormone (TSH) - hyperthyroidism
Adrenocorticotropic hormone (ACTH) – Cushings
Prolactin – hyperprolactinaemia
Follicular stimulating hormone (FSH) & luteinizing hormone (LH) (very rare)
Empty sella
A CSF filled pituitary fossa is a relatively common incidental finding
It may be a manifestation of raised intracranial pressure (e.g. idiopathic intracranial hypertension)
Occasionally it may be associated with hypopituitarism
where is the cavernous sinus
lie within the dural attachments on either side of the body of the sphenoid
inferiorly abut the greater wing of the sphenoid bone.
roof is continuous with the diaphragma sellae, under the chiasm and hypothalamus.
freely intercommunicate via anterior and posterior intercavernous sinuses.
first things affected by cavernous sinus swelling
internal carotid and abducens nerve
Abducens nerve (VI), lies deeper, lateral to internal carotid artery.
Internal carotid artery, first pieces its roof and turns back to lie against it.
nerves in cavernous sinus s
Arranged like a ‘clock face’ Oculomotor nerve (III) Trochlear nerve (IV) Ophthalmic nerve (V1) Maxillary nerve (V2)
Abducens nerve (VI), lies deeper, lateral to internal carotid artery.
Internal carotid artery, first pieces its roof and turns back to lie against it.
what lie above the cavernous sinus
optic tract and uncut of temporal lobe of the cerebrum
there are no valve sin the cavernous sinus
what veins feed into it and where does it go
Receives ophthalmic and superficial middle cerebral veins and sphenoparietal sinus.
Drained by the superior and inferior petrosal sinuses and the pterygoid venous plexus.
Drains into the internal jugular vein via the transverse sinus.
sepsis and thrombosis of cavernous sinus result from what pathogen
staph.a
infections from dangers area of face to via ophthalmic vein which usually drains the facial vein
pterygoid fro deep infections
temporal bone too such as osteomyelitis of the ear
sepsis and the cavernous sinus manifest as
features of sepsis
Cranial nerve palsies (III,IV, Va, Vb, VI)
Consequences of reduction in venous drainage:
facial and periorbital oedema, ptosis, proptosis, chemosis, painful eye movements, papilloedema, retinal venous distension and loss of vision
Caroticocavernous arteriovenous fistula
what happens
Abnormal communication between the internal carotid artery and the cavernous sinus
Causes included base of skull fractures and penetrating injuries, sometimes idiopathic
Clinically manifests as pulsating exophthalmos, ophthalmoplegia, and marked orbital and conjunctival oedema due to increase cavernous sinus venous pressure.
foramen rotundum what nerve
maxillary vein
