Seventh cranial nerve palsy: Lower motor neuron type

53 Seventh cranial nerve palsy


Lower motor neuron type



Instruction


Look at this patient’s face.


Examine the cranial nerves.



Salient features



History




• Onset: whether abrupt followed by worsening over the following day (Bell’s palsy)


• Pain over the preceding or accompanying the weakness (Bell’s palsy)


• The face itself feels stiff and pulled to one side


• Ipsilateral restriction of eye closure


• Difficulty with eating


• Disturbance of taste (caused by chorda tympani fibres)


• Hyperacusis (involvement of stapedius muscle in the inner ear).



Examination




• Weakness of muscles of one half of the face; the patient is unable to screw his or her eyes tightly shut or move the angle of the mouth on the affected side (Fig. 53.1)


• Loss of facial expression


• Widened palpebral fissure.


image

Fig. 53.1 Facial weakness: central (A) and peripheral (B).


Proceed as follows:



• Look for the following when the patient is unaware of being observed:


• Flatter nasolabial folds on the affected side

• Mouth on the affected side droops and participates manifestly less while talking

• The eyelid on the affected side closes just after the opposite eyelid.

• Look at the external auditory meatus for herpes zoster (Ramsay Hunt syndrome)


• Look for parotid gland enlargement


• Examine for taste (loss of taste with the involvement of chorda tympani)


• Check for hearing (for hyperacusis resulting from involvement of the nerve to stapedius muscle)


• Examine tympanic membrane for otitis media


• Tell the examiner that you would like to test the urine for sugar (diabetes).



Diagnosis


The patient has lower motor neuron seventh cranial nerve palsy (lesion), which is idiopathic (aetiology). She is distressed because the condition causes severe disfigurement while talking and has House Brackman grade VI facial palsy (functional status).



Questions




How would you differentiate between upper and lower motor neuron palsy?


In lower motor neuron palsy the whole half of the face on the affected side is involved. In upper motor neuron palsy the upper half of the face (the forehead) is spared (Fig. 53.1).



How is facial palsy graded?


House Brackman grades:



I: normal


II: mild dysfunction, slight weakness, slight synkinesis


III: moderate dysfunction, obvious weakness, incomplete eye closure, normal symmetry only at rest


IV: moderately severe dysfunction


V: severe dysfunction, barely perceptible movement, asymmetry at rest


VI: total paralysis.



Advanced-level questions




What are the causes of bilateral facial nerve palsy?




• Guillain–Barré syndrome (p. 338)


• Sarcoidosis in the form of uveoparotid fever (Heerfordt’s disease)


• Melkersson–Rosenthal syndrome, which is a triad of facial palsy, recurrent facial oedema and plication of the tongue (Hygiea 1928;90:737–41, Z Neurol Psychiatr 1931;131:475–501).


Note: Myasthenia may mimic bilateral facial nerve palsy.

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Dec 4, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Seventh cranial nerve palsy: Lower motor neuron type

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