Optic Chiasm & Visual Pathway Lesions

25, 50

___% of brain tumors occur in the chiasmal area & ___% present w/ the initial complaint of visual loss 

central/normal

orientation of chiasm: optic chiasm directly over pituitary gland

prefixed

orientation of chiasm: optic chiasm anteriorly over tuberculum sellae

postfixed

orientation of chiasm: optic chiasm posteriorly over dorsum sellae

bitemporal hemianopsia

what VF defect is produced w/ a chiasmal lesion if the pt has central/normal orientation?

unilateral monocular VF defect, junctional scotoma, bitemporal hemianopsia 

what VF defects are produced w/ a chiasmal lesion if the pt has postfixed orientation? 

bitemporal hemianopia, homonymous hemianopia

what VF defects are produced w/ a chiasmal lesion if the pt has prefixed orientation?

hemifield slide

w/ complete bitemporal hemianopia, pre-existing phorias may result in separation of the hemifields horizontally or vertically or double vision w/ overlap

temporal, ipsilateral

the nasal VF info is carried by ______ retinal fibers & project to the ________ optic tract

nasal, contralateral 

the temporal VF info is carried by _______ retinal fibers & project to the ______ optic tract 

inferior nasal, anterior

the superior temporal VF info is carried by the _______ retinal fibers in the ______ chiasm

superior nasal, posterior

the inferior temporal VF info is carried by the _______ retinal fibers in the ______ chiasm

benign

is a meningioma benign or malignant?

benign 

is a pituitary adenoma benign or malignant?

benign

is a low grade I pilocytic astrocytoma benign or malignant?

malignant

is a grade II-IV astrocytoma benign or malignant?

malignant

is a oligodendroglioma benign or malignant?

malignant  

is a ependymoma benign or malignant?

malignant

is a mixed glioma benign or malignant?

malignant

is a medulloblastoma benign or malignant?

lung

where is the most common site for secondary brain tumors to come from?

1. HA

2. seizure

3. neurological sx

4. nausea & vomiting 

what are the s/sx of brain tumors? 

1. pituitary tumor

2. craniopharyngioma

3. meningioma

4. glioma

5. aneurysm

what are the etiologies of chiasmal compression?

1. HA

2. blurry vision

3. VF defects

4. diplopia

5. females: amenorrhea, hirsutism

6. males: impotence, gynecomastia, libido loss

what are the s/sx of a pitutiary adenoma?

bitemporal (complete or incomplete), junctional scotoma, homonymous hemianopia (complete or incomplete) 

what are the types of VF defects seen w/ pituitary adenomas? 

nonfunctional (non-secreting) enlargement

type of pituitary adenoma: 25-33%, >70% of large adenomas causing visual loss

hormone hypersecretion (secreting)

type of pituitary adenoma: polactinomas, GH, ACTH, LH, FSH secreting tumors

<10

a microadenoma is ___mm

>10

a macroadenoma is ___mm

prolactinoma & non-secretory tumors

what pituitary adenomas are most likely to have suprasellar extension?

visual loss, hypopituitarism, cranial neuropathies

what s/sx are most common w/ nonfunctional enlargements?

snowman configuration

what is the classic MRI sign of a pituitary macroadenoma on MRI?

1. macroadenoma protruding into sphenoid sinus

2. bone of floor thin & sometimes non-existent

3. enlarged, asymmetric sella

4. erosion of dorsum sella

5. erosion of anterior clinoids

6. extension into cavernous sinus

what are the radiologic features of a pituitary adenoma? 

1. bromocriptine

2. trans-sphenoidal surgery

3. radiation 

what is the tx for a pituitary adenoma? 

directly

the risk of recurrence of a pituitary adenoma is _______ proportional to tumor size

prolactin, TSH, GH, ACTH, LH, FSH, & MSH

what hormones are secreted by the pituitary?

prolactinoma

what is the most common pituitary adenoma?

amenorrhea, galactorrhea, infertility, can increase in size during pregnancy 

what are the specific s/sx of a prolactinoma in women? 

decreased libido, impotence, infertility, hypopituitarism, galactorrhea

what are the specific s/sx of prolactinoma in men?

micro

90% of females dx w/ a prolactinoma are _____

macro

60-80% of males dx w/ prolactinoma are ____

1. primary hypothyroidism → compensatory hyperplasia of TSH cells → enlarged pituitary 

2. TSH secreting tumor → high T3 & T4 

what are the 2 types of TSH-secreting adenoma? 

acromegaly

• GH secreting adenoma in adults

• s/sx:

  • enlargement of hands/feet

  • enlargement of forehead, nose, chin, & lower jaw

  • coarsening of facial features

  • hyperthyroidism

  • diabetes

  • arthritis

  • VF defects

  • HA

gigantism

• GH secreting adenoma in children

• s/sx:

  • growth & height significantly above average

  • longitudinal bone growth still possible

ACTH-secreting adenoma 

• primarily seen in women of childbearing age

• s/sx: 

  • Cushing’s syndrome: truncal obesity, amenorrhea

pituitary apoplexy

• spontaneous, rapid expansion of pituitary due to infarction or hemorrhage

• neuro-ophthalmic emergency

• s/sx:

  • HA sudden & severe

  • sudden VA decrease

  • diplopia due to ophthalmoplegia

  • loss of consciousness

• tx:

  • surgery

  • corticosteroids

  • hormone replacement

meningioma

• most common primary brain tumor

• middle aged women >

• pregnancy stimulates growth

• slowly progressive 

• thought to arise from arachnoidal cap cells 

• s/sx: 

  • asymmetric vision loss

  • nonspecific HA

  • proptosis

  • chemosis

  • engorgement of orbital vasculature

1. exophthalmos

2. disc: normal, edematous, or pale/atrophic

3. optociliary shunt vessels or collaterals at optic disc

what is the classic triad of an optic nerve sheath meningioma?

optic nerve sheath, tuberculum sellae, sphenoid wing, olfactory groove

what are the locations of a meningioma? 

1. hyperostosis

2. no snowman on MRI

describe the appearance of a meningioma on imaging

glioma

• primary astrocytic tumors

• intrinsic tumor infiltrating parenchyma of ON, chiasm, optic tract & radiations, hypothalamus, or 3rd ventricle

grade I pilocytic astrocytoma

• glioma seen in children

• age of onset: 4-8yo

• relatively benign, slowly progressive

• link w/ NF type 1

• s/sx:

  • decreased VA

  • unilateral axial proptosis

  • compressive ON atrophy

  • VF defects

  • hypothalamus dysfunction (growth retardation, diabetes, obesity)

• tx:

  • observation

  • chemotherapy

  • radiation

  • surgery

grade II diffuse astrocytoma

• glioma seen in young adults

• age of onset: 20-40

• infiltrating tumor, slow growing, poorly defined borders

grade III anaplastic astrocytoma or grade IV glioblastoma multiforme

• malignant high grade gliomas seen in adults

• M>F

• middle aged

• s/sx:

  • HA

  • rapid vision loss

  • retro-orbital pain

  • other intracranial signs

• tx:

  • surgery

  • radiation

  • chemotherapy

  • poor prognosis

hypointense

how does a low grade glioma appear on MRI?

contrast enhancement on outside w/ necrosis on inside 

how does a high grade glioma appear on MRI? 

craniopharyngioma

• slow growting benign tumors in suprasellar region

• arise from remnants of Rathke’s pouch

• benign, but locally aggressive

• s/sx:

  • solid + cystic w/ calcification

  • erosion of dorsum sella

  • spreading of anterior & posterior clinoids

• tx:

  • surgery

  • radiation

1. growth retardation

2. delayed sexual development

3. obesity

4. HA & visual difficulty

5. papilledema & hydrocephalus

what are the s/sx of craniopharyngioma in children?

1. diabetes

2. amenorrhea

3. galactorrhea

4. progressive vision loss

5. bitemporal hemianopsia or incongruous homonymous hemianopia 

what are the s/sx of craniopharyngioma in adults?

anerysm 

• location: ICA, OA, ACA, PCA, circle of willis

• rare cause of chiasmal compression 

unilateral monocular VF defect

what kind of VF defect do you get from a lesion at the blue line? 

junctional scotoma

what kind of VF defect do you get from a lesion at the teal line? 

bitemporal hemianopia 

what kind of VF defect do you get from a lesion at the red line? 

bitemporal hemianopia

what kind of VF defect do you get from a lesion at the blue line? 

bitemporal hemianopia 

what kind of VF defect do you get from a lesion at the blue line? 

homonymous hemianopia

what kind of VF defect do you get from a lesion at the green line? 

snowman (pituitary macroadenoma)

snowman (pituitary macroadenoma)

meningioma

optic nerve sheath meningioma

grade I pilocytic astrocytoma

ON glioma

low grade glioma

high grade glioma

craniopharyngioma