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A man in his 30s had been experiencing episodes of partial paralysis of the lower right side of his face for 10 days when he sought medical care, according to a case report in .

The patient said that the episodes of facial muscle weakness each lasted 15 to 30 seconds and then resolved. They began when he awakened from sleep and recurred periodically throughout the day. He described his cognitive state as normal during these episodes, except for a slight slurring of speech occasionally, reported Danielle Eytan, MD, of NYU Langone Health in New York City, and colleagues.

Two years before, he had experienced blurred vision affecting both eyes; this had persisted for 1 month, but he had not seen a physician to investigate it.

In light of the upper motor neuron pattern of paresis, clinicians ordered a CT head scan and a brain MRI.

"Findings revealed extensive nodular, elliptically shaped, and confluent foci of T2-FLAIR (fluid-attenuated inversion recovery) hyperintensity involving the periventricular and subcortical white matter of both hemispheres, corpus callosum, and pericallosal interface," they reported.

At the level of the pons, FLAIR sequence showed no hyperintensity of the right facial nerve nucleus, but there did "appear to be involvement of the left facial colliculus," clinicians explained. The facial nucleus was not involved.

The findings were consistent with a demyelinating process suggestive of multiple sclerosis (MS), Eytan's group said.

The clinician referred the patient to neurologists for further workup. An MRI of the spine showed "patchy segmental areas of signal abnormality throughout the spinal cord," the group observed.

"A diagnosis of MS was made based on the radiographic findings (dissemination in space) and history of visual disturbance suggestive of optic neuritis (dissemination in time)," they explained. Following a confirmed diagnosis of relapsing remitting MS, the patient was treated with ocrelizumab (Ocrevus) infusions.

Discussion

An immune-mediated inflammatory disease of the central nervous system, MS causes demyelination that can result in a wide range of neurologic symptoms.

In reporting this case of MS-related facial nerve palsy, the case authors pointed out that "patients with MS can present with a constellation of symptoms including visual changes, paresis, paresthesias, impaired coordination, and bladder disorders."

Neurologic problems that develop suddenly and resolve quickly tend to be due to seizure or ischemia, the authors noted, as opposed to those caused by demyelinating disease, which tend to develop more gradually and remain unresolved. Previous reports have suggested continuous facial paresis as "the herald symptom for MS," the authors wrote. Unilateral facial paresis -- in some cases misdiagnosed as Bell's palsy -- has been reported as the of MS.

However, Eytan and co-authors believe theirs to be the first reported case of episodic, transient one-sided facial palsy in an MS patient. The pathology behind its episodic rather than persistent nature is not clear, they said.

Facial nerve palsy can be distressing for patients since it can cause unexplained functional and social deficits. The facial nerve extends from the brainstem "to its distal branch points of the facial mimetic muscles." As such, the facial nerve may sustain injury from a wide variety of conditions, including "idiopathic injury (Bell palsy), neoplasm, iatrogenic injury, infection, trauma, and congenital abnormalities," the group explained.

Assessment of a patient with new-onset facial paralysis must determine whether symptoms are due to an upper and lower motor neuron injury, they noted. Paresis that does not involve the forehead is likely due to an upper motor lesion or a peripheral lesion that does not involve the upper division distal branches. "In upper motor neuron paresis, lesions of the corticobulbar tract between the cerebral cortex and pons result in loss of signal in the ventral division of the facial motor nucleus, whereas the dorsal division remains intact from the contralateral nucleus," the authors elaborated.

In suspected Bell's palsy, current clinical practice do not advise routine imaging. However, when a patient presents with facial paresis, physicians are urged to "remain vigilant with a broad differential diagnosis ... and consider MS in the appropriate setting," according to Eytan and colleagues.

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