The trochlear nerve and the superior oblique muscle help us rotate our eyes and look down the stairs. When this nerve gets damaged or diseased it can lead to diplopia, and palsy which are common trochlear nerve disorders.
The trochlear nerve is also called the fourth cranial nerve. It is a motor nerve which stimulates and supplies the superior oblique muscle of the eye. The trochlear nerve is also a part of the cranial nerve which stems from the brain and connect to the eyes. The function of this nerve are interconnected with the superior oblique muscle. Which is also responsible for the movement of the eyes as it is one of the six extra ocular muscles that together help in the movement and alignment of the eyes. There are 3 basic function of the superior oblique muscle which is to firstly roll the eyes downwards, secondly to gaze downwards and thirdly to look away sideways from the centralized downward gaze. When people cannot perform these basic eye movements then it is a sign of serious eye problem or disease that must be immediately checked and treated.
⇨ Vertical Diplopia
This disorder occurs when the trochlear nerve gets damaged due to injury, which weakens the eyes ability to move downwards and also causes double vision. One eye drifts upwards and the other seems relatively oblique. People who suffer from this disorder have to go through the ordeal of seeing two different visions or images at a time from each eye. These images collide or merge into one image that does not make sense to them. Therefore in order to see one clear image these people adopt the head tilt, whereby they tilt their head with their chin tucked in, this helps them to focus on one visual field. Vertical diplopia is even more severe when the eyes look inwards towards the nose.
⇨ Torsional Diplopia
This disorder is another form of trochlear nerve palsy, wherein the eyeballs rotate or roll as per the tilting of the head, thereby letting vertical images remain the way they are. The symptoms of this disorder are very similar to Torticollis or the symptoms of Chronic palsy
⇨ Acute Palsy
Acute palsy is caused due to dysfunction of this nerve. Such dysfunction can be a result of head trauma, because people who have suffered from a brain injury sometimes get this disorder. The symptoms could include blurry vision. While more serious cases could involve displacement of the eye alignment as well as symptoms of diplopia and difficulty in rotating the eyes. These symptoms need vision correction surgical procedures in many cases. Though diseases such as diabetic neuropathy and meningitis can also permanently damage this nerve.
⇨ Chronic Palsy
The trochlear nerve palsy is scientifically also known as the fourth cranial nerve. This is a congenital birth defect wherein the eyes are misaligned vertically due to damage caused to the superior oblique muscle. This damage can occur due to inherent defects in the growth of this muscle that may have weakened it or paralyzed it. Children born with trochlear nerve palsy cannot do the simple eye movements that the superior oblique muscle help in doing and often suffer from inability to look downwards, have hypertropia a condition whereby one eye is misaligned to the other, with one eye being higher than the other. They also have eyes that drift inwards, or where the pupils are closer to the to each others edge. These children look at things with what is called a compensatory had tilt or Torticollis that lets them see an aligned image.
The trochlear nerve is first checked through a neurological examination or a Magnetic Resonance Imaging (MRI) or a Computed Tomography (CT) scan is performed. The ophthalmoscope is the device that the doctor uses to look into the eyes, by which he can check for tumors, damaged blood vessels and whether the pressure inside the skull has increased or not. When the diagnosis is not clear or confusing then the lumbar is punctured through the spinal tap procedure which detects the increase of pressure within the skull as well as to detect if there is an infection. This may need laser eye surgery depending on the seriousness of the case.
Trochlear nerve palsy disorder if diagnosed can be treated. Though surgery is needed in most cases to remove the double vision fields, as the other alternatives rarely mend the disorder completely. Surgery helps to reduce the squint and its angle by enabling both the eyes to coordinate with each other to a larger extent. Eye exercises are also a must for these people and prescribed aftercare is mandatory for effective recovery and desired results.