USMLE Step 1 Neuroanatomy Review 26 08 Hypothalamus (6_6)

USMLE Step 1 Neuroanatomy Review 26 08 Hypothalamus (6_6)


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Begin 26 08 Hypothalamus (6_6) Transcription

Student doctor, what is the name of the tumor that originates from the remnants of Rathke’s pouch?

  • This is a craniopharyngioma.

Now in terms of the tentorium, what type of tumor is the craniopharyngioma?

  • A craniopharyngioma is a supratentorial tumor.

Craniopharyngioma is the most common supratentorial tumor for what patient population?

  • For children.

What syndrome often results from a craniopharyngioma?

  • The hypothalamic syndrome.

Now depending upon what region of the hypothalamus are being pressed on by the growing craniopharyngioma, there can be a wide constellation of symptoms that result. The most common scenario, however, is the hypothalamic syndrome resulting from a craniopharyngioma exerting most of its pressure in which region of the hypothalamus. Upon the tuberal region of the hypothalamus.

What are the four characteristics of the hypothalamic syndrome that are usually present?

  • Obesity, abnormal temperature regulation, diabetes insipidus, and somnolence.

Now the obesity in the hypothalamic syndrome is probably due to pressure from the craniopharyngioma on which nucleus in the tuberal region?

  • The ventromedial nucleus.

And again, what is the ventromedial nucleus also called?

  • It is called the satiety center.

And what condition, similar in some ways to the hypothalamic region, but also specifically different, results from bilateral lesion to the ventromedial nuclei?

  • This particular condition is called hypothalamic obesity.

And to review this, what are the three parts of hypothalamic obesity?

  • Obesity, hyperphagia, savage behavior.

Now the hypothalamic syndrome is different because additional nuclei and additional regions are also involved. While the obesity in the hypothalamic region relates to the pressure on the ventromedial nucleus in the tuberal region, what is the cause of the abnormal temperature regulation in the hypothalamic syndrome resulting from a craniopharyngioma?

And please pause. Well there are actually two possible answers to this question, at least. For example, the anterior nucleus in the supraoptic region is involved in the maintenance of body temperature. Another possibility is the posterior nucleus in the mammillary region, which is involved in thermal regulation, especially heat conservation.

What are likely causes of the diabetes insipidus in the hypothalamic syndrome?

  • The most likely answer would be the paraventricular and supraoptic nuclei in the supraoptic region.

And what is most likely the cause of the somnolence in the hypothalamic syndrome?

  • Probably the suprachiasmatic nucleus in the supraoptic region.

Now that we’ve gone through these four primary characteristics of the hypothalamic syndrome, let’s review them. What are the four characteristics of the hypothalamic syndrome?

  • Obesity, abnormal temperature regulation, diabetes insipidus, and somnolence.

Now it is important to keep in mind that emotional disorders can also have their roots in hypothalamic lesions. Emotional disorders involving hypothalamic lesions usually involves what range of emotions?

  • The range of depression to rage. From a psychological perspective, these are probably most accurately described as mood disorders.

In like manner, hypothalamic disorders can also affect sexual function. What is the most likely general or global result from a hypothalamic lesion that occurs prior to puberty that affects sexual function?

  • Sexual development is most likely arrested.

Hypothalamic lesions that occur after puberty often result in what range of symptoms?

  • Impotence, amennorrhagia, sexual dysfunction.

When a hypothalamic lesion is affecting sexuality, what region is most likely affected?

  • The preoptic region.

What two nuclei are contained in the preoptic region that relate to sexuality?

  • The medial preoptic nuclei and the sexual dimorphic nucleus.

And again, what is the function of the medial preoptic nuclei?

  • To regulate the release of gonadotropic hormone from the adenohypophysis.


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