Assessment of brain stem reflexes
Purpose
Checking the brain stem reflexes in comatose patients determines if the brain stem is intact. Failing any brainstem reflex test indicates significant impairment or damage to the brainstem, which is associated with serious neurological conditions and a poor prognosis.
Cranial nerves throughout the brain stem:
Note the 4 cranial nerves that originate from the pons: cranial nerves (CNs) V, VI, VII, and VIII. All of these emerge from the pontine tegmentum.
Supplies needed to assess brain stem reflexes
- Syringe
- Ice water
- Suction catheter
- Cotton-tipped swab
- Bright light
What are the key nursing assessments for comatose clients?
Key assessments include:
- Vital signs
- Glasgow Coma Scale (GCS) score
- Checking for brain stem reflexes
- Observing for any signs of changes in neurological status
Pupillary reflex
Cranial nerves: II, III
Examination
- Darken the room slightly.
- Use a bright light and shine it in the client’s eye.
- Assess pupil shape, size, and reaction to the bright light.
Expected response
The pupils should directly and consensually constrict in response to the light.
Abnormal response
The pupils staying mid-position and not reacting to the light is considered an abnormal response, indicating damage to the optic or oculomotor nerve or significant brain stem damage.
Corneal reflex
Cranial nerves: III, V, VII
How to check the corneal reflex
- Take a cotton-sip swab or a syringe with saline.
- Either:
- Lightly touch the cornea with the cotton-tip swab, or
- Use a squirt of saline
Expected response
The eyelid should close.
Abnormal response
If the eye does not blink in response to the stimulation, it is a sign of damage to the trigeminal nerve or facial nerve.
Gag reflex + cough reflex
Cranial nerves: IX, X
How to examine the gag and cough reflexes
- Take a suction device or tongue depressor.
- Touch the posterior pharynx with the device. (→ gag reflex)
- Perform endotracheal suctioning. (→ cough reflex)
Expected response
The soft palate elevates, and the client coughs.
Abnormal response
The assessment for the gag and cough reflex is negative if there is no response to the stimulation. The abnormal response suggests damage to the glossopharyngeal and vagus nerves.
Oculocephalic reflex (doll’s eye reflex)
Cranial nerves: III, IV, VIII
How to assess the doll’s eye reflex
Turn the client’s head briskly from side to side.
Expected response
The eyes should move the opposite way the head is turned.
Abnormal response
No eye movement in response to the test indicates severe brain stem damage.
Oculovestibular reflex (cold caloric reflex)
Cranial nerves: III, IV, VI, VIII
Cold caloric test
Instill at least 20 mL of ice water into the client’s ear.
Expected response
The eyes should move laterally toward the affected ear.
Abnormal response
An abnormal response occurs if there is no eye movement, the eyes remaining midline. This significant brain stem injury, particularly involving the vestibulocochlear nerve and brainstem pathways.
Nursing interventions
- Report any abnormalities in brain stem reflexes to the provider.
- Continuously monitor the client’s neurological status and vital signs.
- Supportive care of comatose patients
- Care and education of family members
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