| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (CB) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Description |
Summary: Ophthalmologic Manifestations of Shunt Failure 1. Who can have shunt failure? a. Pediatric patients: usually caused by hydrocephalus b. Adult patients: caused by hydrocephalus or idiopathic intracranial hypertension i. For IAH patients, the most commonly placed shunt is a stereotactically placed programmable valve ventriculoperitoneal shunt. ii. Other shunts include ventriculoatrial shunts and lumboperitoneal shunts. c. Shunt-dependency means that patients cannot maintain appropriate CSF pressure without shunt 2. Ophthalmologic presentation of shunt failure a. Afferent i. Decreased vision ii. May present with papilledema from increased ICP, but not necessary. b. Efferent i. Diplopia ii. Esotropia with an incompetent deviation that's worse in the gaze direction of the paretic muscle 1. May be unilateral or bilateral iii. Dorsal midbrain syndrome 1. Compression of CSF outflow acts like a mass pressing on dorsal midbrain 2. Characterized by lid retraction, convergence, retraction nystagmus, a vertical gaze palsy, and light-near dissociation of the pupils 3. How to test the integrity of the shunt a. CT Scan: first option pursued, in order to observe ventriculomegaly. b. Shunt series: a series of X-rays from head to abdomen that demonstrate that the shunt is properly connected from the skull, through the thorax, to the abdomen i. Cannot indicate whether the shunt is functional or not, but will indicate if the connection is broken. c. Nuclear medicine studies: inject radiolabeled technetium into the shunt itself, and observe whether the radionucleotide ends up in the stomach. If it travels to the stomach, the shunt is at least partially patent. d. MRI: observe transependymal flow e. Spinal tap: determine opening pressure of CSF through a normal spinal tap. High CSF pressure can indicate shunt failure. |
| Transcript |
So today we are going to be talking about the ophthalmologic manifestations of shunt failure and it can either be a shunt that's placed in a kid for hydrocephalus or a shunt that's placed in an adult, either for hydrocephalus or for idiopathic intracranial hypertension, IAH, also known as, pseudotumor cerebri. Shunts come in different flavors: ventriculoperitoneal shunt, ventriculoatrial shunt, lumboperitoneal shunts. At our hospital we prefer stereotactically placed programmable valve ventriculoperitoneal shunts for our higher IAH patients. A lot of our patients come to us and they are shunt-dependent, and what that means is they require the shunt to keep their pressure in an acceptable range, even if the shunt is only partially functional. And the way that shunt failure comes to us as ophthalmologists on the afferent side is with decreased vision, and that decreased vision can be with swollen optic nerve from increased intracranial pressure papilledema, or it can be without a swollen nerve, it could just be a pale nerve. On the efferent side it comes to us as diplopia, and that can be from a non-localizing sign of increased intracranial pressure--a cranial nerve six palsy--and so they're going to have an esotropia with an incompetent deviation that's worse in the gaze direction of the paretic muscle. It can be unilateral or bilateral, and the second efferent way this comes to us is the dorsal midbrain syndrome, so in patients who have dilation of the ventricle, the fourth ventricle, and the aqueduct of Sylvius, if we have a Sylvian aqueduct syndrome with compression of the outflow, we can get dilation of the aqueduct and that will act like a mass pressing on the dorsal midbrain. And the dorsal midbrain syndrome, as you know, is characterized by lid retraction, convergence, retraction nystagmus, especially on attempted up-gaze, a vertical gaze palsy, usually for up-gaze, and light-near dissociation of the pupils. So, if we have vision loss papilledema, a cranial nerve 6 palsy, or the dorsal midbrain syndrome in a patient who has a shunt and is shunt dependent, we should be worried about shunt failure. So those are the ways that shunt failure comes to us, and we're going to be testing the integrity of this shunt, firstly with just a plain CT scan, because if the ventricles are bigger, ventriculomegaly, than they were before, then we know that we have worsening hydrocephalus and neurosurgery has to change or replace the shunt. We can also do a shunt series, which is just a series of x-rays that will show that the shunt is connected from the skull through the neck and down to the thorax and abdomen. That doesn't tell you that it's working, it just tells you it's hooked up, but if it's disconnected or the catheter has rolled up in the abdomen then you know it's broken. And then we have nuclear medicine studies, where we can inject labeled technetium radioisotope into the shunt itself and if we see the radionucleotide appears in the belly, then we know that this shunt is patent and that's at least partially functioning. But the only way to know what the pressure is to measure it, and that means having a spinal tap with an opening pressure. So, if we're worried about shunt function, we're going to examine the patient, we're going to look for papilledema, and the clinical efferent and afferent findings of vision loss in shunt failure patients. We're going to do a CAT scan to look for ventriculomegaly, we might do an MRI scan to look for transependymal flow, we might do the shunt series to make sure it's all connected, and the nuclear medicine study to make sure it's patent. But ultimately, you're going to have to measure the pressure with a lumbar puncture if you're worried if the shunt is working or not. So, an ophthalmologist's role is to check for the afferent and efferent findings to suggest shunt failure in any shunt-dependent patient who's presenting with new symptoms. |
