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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.