Dr Ben Wild
Overview |
There are 12 cranial nerves that form the parasympathetic nervous system that controls the body. Interestingly, most of these nerves affect either the eyes or the eye muscles in some shape or form.
There are two 4th nerves, otherwise known as trochlear nerves. One controls the superior oblique muscle around the right eye and the other controls that same muscle around the left eye.
The superior oblique muscle is responsible for lowering the eye, helping move the eye outwards (towards the ear), and rotating the eyes inwards. When the 4th nerve stops working, aka a 4th nerve palsy, the patient loses control of the superior oblique muscle. This results in sudden vertical double vision which is usually worse when looking towards the normal eye. The double vision usually is lessened with a head tilt towards the shoulder on the same side as the affected eye.
A healthy pair of eyes looking off into the distance.
A right 4th nerve palsy (eye on left (right eye) shows a elevated appearance).
Frontal view of a right eye with attached muscles. The circled muscle represents the superior oblique muscle, which is affected by the 4th nerve palsy.
Signs and Symptoms |
Signs
One eye is elevated when compared to the normal eye. This is made worse by looking towards the normal eye. The patient may have a head tilt.
Symptoms
Vertical double vision that improves when tilting the head towards the opposite shoulder.
Causes and Risk Factors |
Causes
Idiopathic (unknown), congenital (born with this condition), trauma.
Risk Factors
Vascular conditions like high blood pressure, diabetes, brain lesions like tumors or aneurysms, head trauma.
Prevention and Treatment |
Prevention
Ensure a healthy lifestyle to avoid vascular issues like high blood pressure, diabetes, etc.
Treatments
· Needs full neurological work up to identify the cause if it presents as suddenly.
· Usually spontaneously resolves without treatment unless due to aneurysm or tumor.
· Glasses with prism for double vision.
· Surgery for double vision or head tilt.
Prognosis |
In most cases, a 4th nerve palsy resolves on its own. It does require a neurological work up if it occurs suddenly. Symptoms of a 4th nerve palsy can be managed with either surgery or glasses with prism but the underlying cause of the palsy is the more concerning issue.