Sympathetic Nervous System (SNS): Hypothalamus as Sympathetic Output Driver and Horners Syndrome

00:01 When we think about the sympathetics, there is a central controller or a sympathetic output driver to this system of the autonomic nervous system. That output driver is going to be the hypothalamus. We see the hypothalamus here more superiorly. It’s above the spinal cord.

00:19 As a result, it will send out its sympathetic output to influence what is going on within the thoracolumbar area of the spinal cord. By doing so, this is what will activate those preganglionic sympathetic neurons that begin their route out toward their distribution, toward their destination in the lateral gray horns. This output driver can be disrupted along the sympathetics. If that happens, that can result in Horner’s syndrome.

00:57 Horner's syndrome would have to be a disruption of this sympathetic outflow either at C6 here.

01:05 It could be out here at T1. Here’s a disruption here, here, or here with the more superior cervical chain ganglia. At these levels, Horner’s syndrome can or will develop. If it’s inferior to the T1, you can certainly have a disruption but Horner’s syndrome will not be what you’ll see in a patient. So what is Horner’s syndrome? Horner’s syndrome, as a result of this disruption of sympathetic outflow, will be characterized by the three -osis or -oses.

01:40 One member of this family is ptosis. This is where the individual will have a drooping upper eyelid. Miosis is where the individual will have a constricted pupil. Then the last osis here is anhydrosis. This is represented by absence of sweating. A consideration or a cause of Horner’s syndrome in addition to perhaps some lesions along the sympathetic output, this is fairly common when one is thinking about some exam questions that might be related to Horner’s syndrome. This is where an individual could have a Pancoast lung tumor. A Pancoast lung tumor will extend between the lung itself and the posterior aspect in which the lung resides along the posterior body wall and can extend upwards here and start to involve sympathetic related structures that would then result in this particular syndrome.