Optic Chiasm and Pituitary Anatomy Quiz
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Questions and Answers

What percentage of brain tumors occur in the chiasmal area?

  • 25% (correct)
  • 10%
  • 75%
  • 50%

    • What is the most common type of pituitary adenoma?

  • Nonfunctional (non-secreting) (correct)
  • Prolactinoma
  • Adenoma associated with visual loss
  • Growth hormone secreting

    • Which visual field defect is most commonly associated with pituitary adenomas?

  • Homonymous hemianopia
  • Bitemporal hemianopia (correct)
  • Central scotoma
  • Monocular vision loss

    • In which position does the optic chiasm sit in the majority of cases?

    <p>Central over the pituitary gland (B)</p> Signup and view all the answers

    What is the primary treatment for a prolactinoma?

    <p>Bromocriptine (B)</p> Signup and view all the answers

    What treatment is commonly used for pituitary adenomas?

    <p>Trans-sphenoidal surgery (D)</p> Signup and view all the answers

    Which of the following symptoms is most commonly associated with GH-secreting adenomas in adults?

    <p>Acromegaly (D)</p> Signup and view all the answers

    Which condition is primarily caused by excess ACTH secretion?

    <p>Cushing’s Disease (A)</p> Signup and view all the answers

    Which type of tumor accounts for about 20-25% of chiasmal compressions?

    <p>Craniopharyngioma (A)</p> Signup and view all the answers

    What characterizes TSH-secreting adenomas?

    <p>Thyrotoxicosis with elevated T3 and T4 (A)</p> Signup and view all the answers

    Which radiological feature is typically associated with a macroadenoma?

    <p>Protrusion into the sphenoid sinus (D)</p> Signup and view all the answers

    Which symptom is NOT typically associated with pituitary apoplexy?

    <p>Chronic fatigue (D)</p> Signup and view all the answers

    What is the primary hormone secreted by the anterior pituitary gland that stimulates the adrenal cortex?

    <p>Adreno-corticotropic hormone (ACTH) (A)</p> Signup and view all the answers

    What is the common origin of craniopharyngiomas?

    <p>Pituitary gland embryonic tissue (C)</p> Signup and view all the answers

    What is a potential effect of Sheehan's syndrome?

    <p>Hypopituitarism (C)</p> Signup and view all the answers

    Which imaging modality is primarily used to diagnose aneurysms that may cause chiasmal compression?

    <p>CT scan and arteriography (D)</p> Signup and view all the answers

    Study Notes

    Optic Chiasm

    • 25% of brain tumors occur in the chiasmal area of the thalamus.
    • Approximately 50% of these tumors present with initial visual loss complaints.

    Anatomy: Chiasm & Pituitary

    • The pituitary gland is situated within the sella turcica of the sphenoid bone.
    • The diaphragma sellae is a layer of dura mater.
    • The optic chiasm is positioned about 10mm above the diaphragma sellae.
    • Measurements:
      • 15mm
      • 8mm
      • 4mm
      • 45°
      • 10mm

    Position of Optic Chiasm

    • Central (80%): The chiasm sits directly above the pituitary gland.
    • Prefixed (10-16%): The chiasm sits in front of the pituitary gland; affects the chiasm and optic tracts.
    • Postfixed (4-10%): The chiasm sits behind the pituitary gland; affects the chiasm and optic nerves.

    Etiologies of Chiasmal Compression

    • Pituitary tumor (50-55%)
    • Craniopharyngioma (20-25%)
    • Meningioma (10%)
    • Glioma (7%)
    • Aneurysm (rare)

    Pituitary Adenoma

    • Headache
    • Blurred vision (vague)
    • Visual field (VF) defects
      • Bitemporal(superior > inferior)
      • Junctional scotoma
      • Incongruous homonymous hemianopia
      • Diplopia
      • "hemi-field slide"
    • Two groups:
      • Nonfunctional (non-secreting): accounts for 40%, 70% macroadenomas cause visual loss.
      • Hormone hypersecretion: prolactinomas and Growth Hormone are most common.
    • Radiological features:
      • Macroadenoma protruding into the sphenoid sinus.
      • Thin bone of the floor or non-existent.
      • Enlarged, asymmetrical sella turcica.

    Pituitary Adenoma: Treatment

    • Surgery: trans-sphenoidal
    • Radiation: Gamma Knife, Proton Beam.
    • Medical therapy: Bromocriptine, Octreotide

    Pituitary Gland: Hormones

    • Anterior Pituitary:
      • Adreno-corticotropic hormone (ACTH)
      • Growth Hormone (GH)
      • Melanocyte Stimulating Hormone (MSH)
      • Thyroid Stimulating Hormone (TSH)
      • Gonadotropins (FSH, LH)
      • Prolactin
    • Posterior Pituitary:
      • Oxytocin
      • ADH

    Prolactinoma

    • 35% of all pituitary tumors.
    • Secretes prolactin 100–1000x normal levels.
    • Women: amenorrhea, galactorrhea, infertility
    • Men: decreased libido, impotence, infertility, hypopituitarism, galactorrhea, gynecomastia.
    • Treatment (1st line): Bromocriptine, Cabergoline

    TSH-Secreting Adenoma

    • Rare; ~50% with VF defects.
    • Two types:
      • Primary hypothyroidism leads to hyperplasia of pituitary thyrotroph cells and enlarged pituitary gland.
      • TSH-secreting tumor leads to thyrotoxicosis—high circulating levels of T3 and T4.
    • Thyroid Ophthalmopathy is rare.

    GH-Secreting Adenoma

    • Secretes excess growth hormone.
    • Adults: acromegaly (enlarged hands/feet, lower jaw/tongue, coarsened facial features).
    • Children: gigantism.
    • Associated symptoms: hyperthyroidism, diabetes, arthritis.

    ACTH-Secreting Adenoma

    • Secretes excess ACTH.
    • Hormone responsible for cortisol production.
    • Cushing's disease:
      • Truncal obesity
      • Thin skin and purple striae
      • “Moon face”, “Buffalo Hump”
    • Small tumors.
    • Rarely cause chiasmal compression.

    Pituitary Apoplexy

    • Spontaneous, rapid pituitary gland expansion (infarction or tumor).
    • Neuro-ophthalmic emergency.
    • Symptoms:
      • Sudden and severe headache
      • Visual loss/visual field deficits
      • Diplopia
      • Nausea, vomiting
    • Often occurs with pituitary tumors; ~80% do not know they have pituitary tumor.
    • Sheehan's syndrome.

    Craniopharyngioma

    • ~3% of intracranial tumors; 13.5% of CNS tumors in children.
    • Derived from pituitary gland embryonic tissue.
    • Slow-growing tumors (suprasellar region)
    • Can be solid, cystic, or a combination.
      • Hypothalamus dysfunction:
      • Children (<15): Growth retardation, delayed sexual development, obesity, HA, visual symptoms, papilledema and hydrocephalus
      • Adults (50-70 year olds): Endocrine dysfunction (diabetes, amenorrhea, galactorrhea), progressive vision loss, papilledema is uncommon, VF defects, bitemporal hemianopia, incongruous homonymous hemianopia.
    • Radiological features:
      • VF defect
      • Suprasellar calcification (50-70%)
      • Odontogenic cells
      • Often benign
      • Surgery is difficult
      • Radiation treatment
      • Recurrences common

    Meningioma

    • Middle-aged women (pregnancy stimulates growth).
    • Arise from arachnoidal cap cells (multi-lobed).
    • Slowly progressive; malignant or benign.
    • Location:
      • Optic nerve sheath (exophthalmos, chronic disc edema, followed by atrophy, collateral vessels)
      • Tuberculum sellae (junction of chiasm and optic nerve)
      • Lateral portion of sphenoid bone
      • Olfactory groove
      • Loss of smell.
    • Signs & Symptoms:
      • Asymmetric vision loss
      • Nonspecific headache
      • Proptosis, chemosis, engorgement of orbital vasculature
      • Optic disc (normal, papilledema, pallor)
      • Chiasm: asymmetrical VF defect
      • Radiologic features: hyperostosis
      • Treatment: surgery, radiation

    Glioma

    • Primary astrocytic tumors.
    • Infiltrate optic nerve, optic tract, radiations, hypothalamus, 3rd ventricle.
    • 70% of optic pathway gliomas develop symptoms by the 1st decade of life; 90% are detected by the 2nd decade.
      • Categories include
        • Grade 1 pilocytoma
        • Grade 2 astrocytoma
        • Grade 3 anaplastic astrocytoma
        • Grade 4 glioblastoma multiforme
    • Glioma Children
      • Pilocytic Astrocytoma
      • Onset 4–8 years
      • Relatively benign
      • Slowly progressive
      • Ocular S/Sx include decreased visual acuity, unilateral eye proptosis, optic nerve atrophy, and visual field (VF) defects.
    • Glioma Children Radiological features
      • Double-intensity tubular thickening of optic nerve, pseudo-CSF, and optic nerve kinking.
      • Optic Nerve Features include NF-1 patients, enlargement of the chiasm, infiltration of the hypothalamus.
    • Glioma Adults
      • Rare and include malignant high-grade glioblastomas
      • Middle aged, male>female
      • Headache, rapid onset vision loss, retro-orbital pain.
      • Optic nerve edema/optic nerve atrophy
      • Treatment: surgery, radiation, chemotherapy.
      • Poor prognosis

    Aneurysm

    • Location:
      • ICA
      • OA
      • ACA
      • PCA
      • Circle of Willis
    • Rare cause of chiasmal compression.
    • Diagnosis involves CT scan and arteriography.

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    Related Documents

    Optic Chiasm Slides PDF

    Description

    Test your knowledge on the anatomy of the optic chiasm and its relationship with the pituitary gland. This quiz covers key aspects such as its position variations, common pathologies, and the implications of chiasmal compression. Perfect for students studying neuroanatomy or related fields.

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