Bell's palsy pathophysiology

Bell's palsy Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Mohamadmostafa Jahansouz M.D.[2]

Overview

The exact pathogenesis of [disease name] is not fully understood.

OR

It is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].

OR

[Pathogen name] is usually transmitted via the [transmission route] route to the human host.

OR

Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.

OR

[Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].

OR

The progression to [disease name] usually involves the [molecular pathway].

OR

The pathophysiology of [disease/malignancy] depends on the histological subtype.

Pathophysiology

Pathogenesis

• It is understood that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].
• [Pathogen name] is usually transmitted via the [transmission route] route to the human host.
• Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.
• [Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].
• The progression to [disease name] usually involves the [molecular pathway].
• The pathophysiology of [disease/malignancy] depends on the histological subtype.

Genetics

• [Disease name] is transmitted in [mode of genetic transmission] pattern.
• Genes involved in the pathogenesis of [disease name] include [gene1], [gene2], and [gene3].
• The development of [disease name] is the result of multiple genetic mutations.

Gross Pathology

• On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Microscopic Pathology

• On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Pathophysiology

Microscopic Pathology

• The facial nerve has an edematous, thickened perineurium with infiltrates of inflammatory cells between nerve bundles and around blood vessels.
• It appears that the histology of the facial nerve in Bell's palsy is similar to Herpes Zoster infection, suggestive of an infectious cause.

Associated Conditions

Bell’s Palsy-induced Blepharospasm

Blepharospasm associated with Bell's palsy has been rarely reported. Instead of the classic presentation with the affected eye wide open, the affected eye is closed shut, with the patient unable to open it (Blepharospasm).

• So far, seven patients previously reported: all women.
• In five of the seven patients, blepharospasm appeared within a month after the onset of Bell’s palsy.

Possible Mechanisms

• The majority of patients with blepharospasm have a high incidence of local ocular symptoms prior to or at the onset of blepharospasm, such as blepharitis, conjunctivitis, dry eyes or photophobia.
• Chronically disturbed sensory inputs to the central nervous system due to lagophthalmos and corneal irritation may contribute to the generation of blepharospasm.
• In patients with Bell’s palsy, there is an enhanced blink reflex secondary to inputs from the paralyzed side compared which those of the non-paralyzed side.
• Abnormal afferent input from the paralyzed side contributes to the abnormal sensitization of the blink reflex, thus facilitating the induction of abnormal facial motor outputs such as blepharospasm.
• It is unclear why Bell’s palsy-induced blepharospasm is extremely rare.

References

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