Cranial Nerve Tests | Nervous System

Summary

This video provides an in-depth guide on testing the 12 cranial nerves, which control various sensory and motor functions related to the head, neck, and beyond. Each nerve's function is explored, from the olfactory nerve for smell to the hypoglossal nerve for tongue movement. The video outlines both sensory and motor components, offering practical tests for each nerve, such as vision checks, facial expression assessment, and hearing tests. It also includes mnemonics to remember the order and function of the cranial nerves, making the information easy to recall for healthcare professionals and students.

Takeaways

• 😀 The cranial nerves consist of 12 pairs, each having distinct functions related to sensory, motor, or both.
• 😀 The olfactory nerve (cranial nerve 1) controls the sense of smell, and light floral scents are best for testing.
• 😀 The optic nerve (cranial nerve 2) is involved in vision, and its functionality can be tested through acuity tests or the pupillary reflex.
• 😀 Oculomotor (cranial nerve 3), trochlear (cranial nerve 4), and abducens (cranial nerve 6) are responsible for eye movements, including pupil constriction, eyelid elevation, and lateral eye movement.
• 😀 Testing eye movement for cranial nerves 3, 4, and 6 can be done with the H movement test, where the patient follows a finger in different directions.
• 😀 The trigeminal nerve (cranial nerve 5) has both sensory and motor functions, with sensory aspects involving sensation across the face, and motor aspects involving chewing.
• 😀 The facial nerve (cranial nerve 7) controls facial expressions and the sense of taste in the front two-thirds of the tongue.
• 😀 The vestibular cochlear nerve (cranial nerve 8) is responsible for hearing and balance.
• 😀 The glossopharyngeal nerve (cranial nerve 9) is both sensory and motor, contributing to taste in the back third of the tongue and aiding in swallowing.
• 😀 The vagus nerve (cranial nerve 10) extends beyond the head and neck to control functions like the heart, airways, and digestive system; it is primarily sensory.
• 😀 The accessory nerve (cranial nerve 11) is motor and controls shoulder shrugging, and the hypoglossal nerve (cranial nerve 12) controls tongue movement.

Q & A

What are the 12 pairs of cranial nerves, and how can they be remembered?

The 12 pairs of cranial nerves are olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, and hypoglossal. An easy mnemonic to remember them is: 'Oh, Oh, Oh, To Touch And Feel Very Good Velvet, Ah Heaven'.

How can you differentiate between sensory, motor, and both sensory-motor cranial nerves?

To remember which cranial nerves are sensory, motor, or both, you can use the mnemonic: 'Some Say Mary Mummy But My Brother Says Big Brains Matter Most'. 'S' stands for sensory, 'M' for motor, and 'B' for both.

What does the olfactory nerve do, and how is it tested?

The olfactory nerve is responsible for the sense of smell. It can be tested by asking the patient to smell light floral or coffee scents, avoiding strong or noxious odors that might trigger the trigeminal nerve and cause a false result.

How do you test the optic nerve?

The optic nerve can be tested through visual acuity (e.g., reading a Snellen chart), the four fields of vision, or a pupillary reflex test. The pupillary reflex involves shining a light into the eye and checking for pupil constriction.

What is the function of the oculomotor nerve, and how can it be tested?

The oculomotor nerve controls eyelid elevation, eye movement (up, down, and inward), and pupil constriction. It can be tested by checking for ptosis (drooping eyelid), performing an eye movement test (H-pattern), or testing the pupillary reflex.

What is the role of the trochlear nerve in eye movement?

The trochlear nerve controls the muscle that pulls the eye down and inwards. If not functioning properly, individuals may tilt their head to compensate for the loss of function.

How does the abducens nerve affect eye movement?

The abducens nerve controls the lateral movement of the eye. If it isn't working, the eye will move inward and downward, which can be observed during eye movement testing.

What is the function of the trigeminal nerve, and how can it be tested?

The trigeminal nerve is both sensory and motor. Sensory testing involves feeling different areas of the face (ophthalmic, maxillary, mandibular regions), while motor testing involves checking jaw movements and muscle resistance when the jaw is opened.

How do you test the facial nerve's sensory and motor functions?

The facial nerve's motor function can be tested by assessing facial expressions (e.g., raising eyebrows, smiling). Sensory testing involves the sense of taste on the front two-thirds of the tongue.

What is the function of the vagus nerve, and how can it be tested?

The vagus nerve controls various functions beyond the head and neck, including the heart, airways, and digestive system. It can be tested through the gag reflex, as it plays a role in swallowing.