The fourth cranial nerve (trochlear nerve) has the longest intracranial course; it is the only cranial nerve that has a dorsal exit from the brainstem (figure 1). It begins in the midbrain at the level of the inferior colliculus as fascicles extending from the fourth nerve nuclei.
Which cranial nerve has shortest intracranial course?
The trochlear nerve is the fourth paired cranial nerve. It is the smallest cranial nerve (by number of axons), yet has the longest intracranial course. It has a purely somatic motor function.
Which cranial nerve is the longest one?
1 Answer. Mandira P. Xth cranial nerve, Vagus, is the longest among all cranial nerves.
Which cranial nerve is commonly affected by increase in intracranial pressure?
As the abducens nerve enters the subarachnoid space, other etiologies may arise resulting in palsy. In these cases, the palsy is primarily because of the increased intracranial pressure. As such, other symptoms such as a headache, nausea, vomiting, and papilledema may be noted.
What does the 4th cranial nerve control?
The fourth cranial nerve controls the actions of one of the external eye muscles, the superior oblique muscle. This muscle runs from the back of the eye socket to the top of the eye. It passes through a loop of tissue near the nose known as the trochlea. It turns the eye inward and downward.
What is the smallest cranial nerve?
The trochlear nerve is the fourth cranial nerve (CN IV) and one of the ocular motor nerves that controls eye movement. The trochlear nerve, while the smallest of the cranial nerves, has the longest intracranial course as it is the only nerve to have a dorsal exit from the brainstem.
What is the shortest nerve in the body?
It is the smallest nerve in terms of the number of axons it contains. It has the greatest intracranial length. It is the only cranial nerve that exits from the dorsal (rear) aspect of the brainstem.
|Anatomical terms of neuroanatomy|
Which is the thickest cranial nerve?
The largest cranial nerve is trigeminal nerve. The smallest cranial nerve is abducens nerve. The thinnest cranial nerve is trochlear nerve.
Which is the longest nerve in human body?
The sciatic nerve is the largest nerve in your body. It begins in your lower back and travels all the way down to the heel of your foot. You may have heard of a condition called sciatica in which painful sensations radiate from your lower back and down your leg.
Which cranial nerve has highest number of branches?
Vagus nerve has the highest number of branches.
Which is the sixth cranial nerve?
Cranial nerve six (CN VI), also known as the abducens nerve, is one of the nerves responsible for the extraocular motor functions of the eye, along with the oculomotor nerve (CN III) and the trochlear nerve (CN IV).
How do you test for cranial nerve 6?
3rd, 4th, and 6th Cranial nerves
Extraocular movements controlled by these nerves are tested by asking the patient to follow a moving target (eg, examiner’s finger, penlight) to all 4 quadrants (including across the midline) and toward the tip of the nose; this test can detect nystagmus and palsies of ocular muscles.
How do you test cranial nerve 6?
Cranial nerve VI controls eye movement to the sides. Ask the patient to look toward each ear. Then have him follow your fingers through the six cardinal fields of gaze. Here’s another easy technique you can use: With your finger, make a big X in the air and then draw a horizontal line across it.
How long does cranial palsy last?
Some cases may resolve on their own, and the ophthalmologist will usually wait at least 6 months for possible spontaneous improvement.
How do you test for 4th nerve palsy?
Features suggestive of a bilateral fourth nerve palsy include:
- Alternating hypertropia on horizontal gaze or tilt.
- Positive Bielschowsky head tilt test to either shoulder.
- Large degree of excyclotorsion (> 10 degrees)
- Absent or small hypertropia in primary gaze.
- Underaction of both superior obliques on duction testing.
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How common is 4th nerve palsy?
Of 4,373 acquired cases of extraocular muscle palsy in adults, there were only 657 cases of isolated fourth nerve disease. Fourth nerve palsy was also the least frequent in pediatric population. In a similar Mayo Clinic study of 160 children, 19 of them had isolated fourth nerve palsy.