Ophthalmological
Optical coherence tomography (OCT)
- Uses light to provide high resolution images of the retina thickness (including the optic disc)
- Might have some prognostic information
- Thinning or atrophy of
- Retinal nerve fibre layer
- Thins after
- Ganglion cell complex
- Thins first before visual field loss
- Can see ganglion cell thinning first
- 2 to 3months to see thinning to occur
Visual field testing
- Confrontation
- Do 4 quadrants with colour as a fast check
- Do blind spot check with red pin as blind spot increases with papillodema
- Absolute and relative scotoma
- Red hat pin
- Relative scotoma
- Magnocellular pathways
- White hat pin
- Absolute scotoma
- Parvocellular pathways
- By perimetry with a tangent screen
- Use the small red stimulus since desaturation of colour is an early sign of chiasmal compression
- Types
- 160 degree testing
- HVF requires good patient cooperation to be valid
- False negative: asleep
- False positive: trigger happy
- Central 60 degree
- Has SD results
Goldman perimetry
The blind spot is incoorporated into the Superior temporal and nasal quadranopia.
Together with the right eye. The patient has a Right homonymous heminanopia that is incongruent (i.e. one is upper and one is lower quadrant)
Blue line is the outer isomere.
The 3 lines have different light intensity and light size.
This image is of the right eye visual field as the n shaped blind spot is on the temporal side (the right side here)
Automated Humphrey perimeter
See Pituitary eye assessment
- Estermann driving standards
Visual deficit pattern
- Depends on the location of chiasm in relation to the sella turcica
- Most chiasm above sella
- Compression of optic chiasm (when chiasm above sella)
- Bitemporal hemianopsia with macular splitting (most common)
- Rare: monocular temporal hemianopsia
- Start to give you superior quadranopia first because the inferior chiasmic fibres get compressed from the rising tumour from the sellar
- 4% chiasm Posterior to sella (postfixed chiasm)
- Compression of optic nerve (postfixed chiasm)
- Ipsilateral vision loss + contralateral superior temporal quadrantanopsia
- Compression of the anterior knee of Wilbrand
- Central scotoma or Monocular reduction in visual acuity
- 8% chiams anterior to sella (prefixed chiasm)
- Compression of optic tract (prefixed chiasm)
- Homonymous hemianopsia
Ancillary visual testing
- Visual evoked potentials: limited use
Endocrine
- 8 A.M. cortisol is the best test for hypocortisolism (e.g. to look for pituitary insufficiency); 24-hour urine free cortisol is the best for hypercortisolism (e.g. to look for Cushing’s syndrome)
- IGF-1 is the primary test for excess growth hormone (GH); direct measurement of GH is unreliable
- Aim
- Aid diagnosis of tumour type
- Determines whether any hormones needs replacing
- Serves as a baseline for comparison after treatment.
- Selective loss of a single pituitary hormone together with thickening of the pituitary stalk is strongly suggestive of autoimmune hypophysitis
- Thyroid axis
- Gonadal axis
- Screening:
- Serum gonadotropins:
- FSH & LH
- Sex steroids:
- Oestradiol in women
- Testosterone in men (measure total testosterone)
- Further testing:
- None dependable in differentiating pituitary from hypothalamic disorders
- Prolactin levels (PRL):
- For prolactinoma if >10x your normal value
- Neurohypophysis (posterior pituitary): deficits are rare with pituitary tumors
- Screening:
- Check adequacy of ADH by demonstrating concentration of urine with water deprivation
- Further testing:
- Measurement of serum ADH in response to infusion of hypertonic saline
Endocrine screening: | Rationale |
8 A.M. cortisolᵃ & 24-hour urine free cortisolᵃ | ↑ Cortisol in hypercortisolism (Cushing syndrome); ↓ Cortisol in hypoadrenalism (primary or secondary) |
Free T4ᵇ, TSH (alternatively, total T4 may be used, if preferredᵇ) | Hypothyroidism: ↓ T4 & ↑ TSH in primary hypothyroidism (this may cause thyrotroph hyperplasia in pituitary gland); ↓ T4 & TSH nl or ↓ in secondary hypothyroidism (as in hypopituitarism) Hyperthyroidism (thyrotoxicosis): ↑ T4 & ↓ TSH (primary) in primary hyperthyroidism; ↑ T4 & ↑ TSH in TSH-secreting pituitary adenomas |
Prolactin | ↑ or ↑↑ with prolactinoma; slight ↑ with stalk effect (usually <90 ng/ml) |
Gonadotropins (FSH, LH) and sex steroids (♀: estradiol, ♂: testosterone) | ↓ in hypogonadotropic hypogonadism (from mass effect causing compression of pituitary gland); ↑ with gonadotropin-secreting adenoma |
Insulin-like growth factor-1 (IGF-1) AKA somatomedin-Cᵇ | ↑ in acromegaly; ↓ in hypopituitarism (one of most sensitive markers) |
Fasting blood glucose | ↓ in hypoadrenalism (primary or secondary) |
Radiographic imaging
General
- MRI without and with contrast with dedicated images through the pituitary spaced 1–2mm apart is the imaging modality of choice
- 3T more clearer than 1.5T
- If MRI contraindicated: CT without & with contrast (with coronal reconstruction) + cerebral angiogram
- Thin cut CT through the sella/sphenoid region and/or CTA may be used to augment the MRI (or may be used in cases where MRI is contraindicated)
- Problems with imaging
- 50% of pituitary tumors causing Cushing’s syndrome are too small to be imaged on CT or MRI (therefore endocrinologic testing is required to prove the pituitary origin)
- Imaging can't differentiate intrasellar lesions
- Normal AP diameter of pituitary gland:
- Female of childbearing age (≈ 13–35 yrs): ≤ 11mm
- Everyone else ≤9mm is normal
- Pituitary glands in adolescent girls may be physiologically enlarged (mean height: 8.2 ± 1.4mm) as a result of hormonal stimulation of puberty.
MRI imaging
- Type of scan required
- Typical order
- Brain MRI +C and -C
- Pituitary MRI +C and -C
- Should include thin coronal cuts thru sella showing cavernous sinus and chiasm
- Hunting for microadenoma
- Dynamic MRI: tumour might enhance differently than the gland
- Gd given within 5mins of scan
- Initially Gd enhances the Pituitary gland (lack of BBB) and not the tumour however after 30mins the tumour enhances
- For follow up macroadenomas
- Routine coronal & sagittal pituitary MRI without & with contrast suffices
- Findings
- Variable: 75% are low signal on T1WI, and high signal on T2WI (but 25% can behave in anyway, including completely opposite to above)
- Neurohypophysis:
- Normally is high signal on T1WI (possibly due to phospholipids).
- Absence of this “bright spot” often correlates
- Diabetes insipidus
- Autoimmune hypophysitis
- Pituitary stalk
- Deviation of the pituitary stalk may also indicate the presence of a microadenoma.
- Normal thickness of the pituitary stalk is approximately equal to basilar artery diameter.
- Thickening of stalk is usually NOT adenoma;
- Differential diagnosis for a thickened stalk: lymphoma, autoimmune hypophysitis, granulomatous disease, hypothalamic glioma.
CT
- Superseded by MRI
- Useful when
- Contraindicated for MRI
- Consider also CTA to demonstrate parasellar carotid arteries and to R/O giant aneurysm as a diagnostic possibility
- Want to characterize sphenoid septal anatomy
- Calcium in pituitary usually signifies haemorrhage or infarction within tumor.
DSA
- CTA
- MRI is good enough to visualise vessel so not routinely needed
Made with Bullet