Cranial Nerve Reflexes

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Ciliary reflex

Take a cotton swab and touch the ciliary body of the eye. If the patient doesn't blink, the patient has brain stem injury (fifth nerve nucleus is in the brain stem).

Deviating jaw:

Fifth nerve injured. Jaw deviates to paralyzed side.

Jaw reflex:

Ask the patient to open their mouth and then you tap on their chin gently; the jaw closing down powerfully signifies an upper motor neuron lesion of the fifth nerve.

Sixth nerve involvement:

The sixth nerve is the most common injured nerve because it has the longest pathway in the brain.

Patient cannot look to the sides:

Sixth nerve involvement.

Patient cannot look down:

Superior oblique muscle paralyzed.

Seventh nuclear involvement:

Supra-nuclear nerve involvement means a stroke; infra-nuclear nerve involvement means Bell's palsy. It is very important to differentiate between infra-nuclear and supra-nuclear seventh nerve involvement. If it is a supra-nuclear seventh nerve involvement, it is going to spare the upper of the face (only lower-half of the face involved). An infra-nuclear lesion will involve the whole face. Thus, forehead spared is supra-nuclear; forehead involved in infra-nuclear. Another way to differentiate is using the eyes. Ask the patient to close their eyes; if you can forcefully open the eyes, it is infra-nuclear; if you cannot forcefully open the eyes, it is supra-nuclear.

Regurgitation from the nose:

Tenth nerve involvement.

Shrug shoulders:

Test for eleventh nerve.

Patient sticks out tongue:

Twelfth nerve ok.

Deviations of tongue and jaw:

CN 5, 7, and 12 (PNP sandwich) cause deviations of any kind. CN 5 lesion causes mouth to deviate toward the paralyzed side; CN 7 lesion causes angle of the mouth to deviate toward normal side; CN 12 lesion causes tongue to deviate toward paralyzed side.

Additional Reading:

Random USMLE Facts

1. Random USMLE Facts volume 1-1
2. Random USMLE Facts volume 2-1
3. Random USMLE Facts volume 3-1
4. Random USMLE Facts volume 4-1
5. Random USMLE Facts volume 5-1
6. Random USMLE Facts volume 6-1
7. Random USMLE Facts volume 7-1
8. Random USMLE Facts volume 8-1
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11. Random USMLE Facts volume 11-1
12. Random USMLE Facts volume 12-1

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1. General Examination for Internal Medicine
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3. ER Chest Pain Workup
4. Format for Patient Presentation
5. Pulmonary Examination for Internal Medicine
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9. Motor System Examination
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