Interactive Transcript
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This is an MRI of the brain in a
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14-year-old with short stature,
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also with some vision abnormalities.
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On the axial T2-weighted image,
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we see the absence of the septum pellucidum.
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The lateral ventricles otherwise
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look fairly normal,
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but there is no intervening septum pellucidum.
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The brain otherwise looks relatively normal,
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other than in the anterior aspect of the left
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middle cranial fossa,
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we have an arachnoid cyst,
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which is a normal variant.
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If we look in this coronal image,
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we see very small optic nerves in the posterior
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orbital segment of the optic nerves,
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with surrounding prominence of the CSF
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in the optic nerve sheath.
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Those are signs of optic nerve hypoplasia.
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If we look at the sagittal T1-weighted image,
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we see a very small optic chiasm.
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So a small optic chiasm,
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small optic nerves,
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and absence of the septum pellucidum
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are the features of septo-optic dysplasia.
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But this individual has one other finding that
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can be associated with septo-optic dysplasia
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that we need to be aware of.
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If we look here, this is the sella turcica,
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and this here is the adenohypophysis.
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Normally,
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at the posterior adenohypophysis,
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there's a neurohypophyseal area of T1 shortening
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or the posterior pituitary bright spot.
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We don't see a posterior pituitary bright spot.
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We also don't see a pituitary infundibulum.
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But what we do see is at the expected location
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of the infundibular recess of the third
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ventricle, we see a bright globular area here.
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This is an ectopic neurohypophysis.
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The neurohypophysis,
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which normally migrates down
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from the hypothalamus,
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down along with the development of the pituitary
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infundibulum to end up along the posterior
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aspect of the pituitary gland, never migrated.
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Interestingly, this is an abnormality that,
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from an endocrinologic standpoint,
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usually has little to no posterior
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pituitary dysfunction.
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The dysfunction is actually related to the
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anterior pituitary because given the lack of
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migration of the posterior pituitary
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down to the sella turcica,
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the pituitary infundibulum doesn't form.
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And when the pituitary infundibulum
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doesn't form,
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the hypothalamic hypophyseal portal venous
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system does not form.
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And so, therefore,
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the releasing hormones from the hypothalamus
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never reach the pituitary gland,
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so the pituitary gland is understimulated,
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and therefore,
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you have adenohypophyseal dysfunction,
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which can manifest with things such as
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short stature and abnormalities with puberty.
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