Can a parotid abscess cause lower motor neuron (LMN) facial palsy?

Can Parotid Abscess Cause LMN Facial Palsy?

Yes, parotid abscess can cause lower motor neuron (LMN) facial palsy, though this is an extremely rare complication that occurs through direct compression or inflammation of the facial nerve as it courses through the parotid gland.

Mechanism of Facial Nerve Involvement

The facial nerve (CN VII) exits the temporal bone at the stylomastoid foramen and courses directly through the parotid gland before branching to innervate all ipsilateral facial muscles 1. When a parotid abscess develops, the resulting inflammation and mass effect can compress or directly involve the facial nerve within the gland, producing a complete lower motor neuron facial palsy that affects the entire ipsilateral side of the face, including the forehead 1.

Clinical Evidence and Rarity

• Literature review reveals only approximately 15-16 documented cases of facial nerve palsy associated with suppurative parotitis or parotid abscess, making this an exceedingly rare complication 2, 3, 4.
• Case reports have documented parotid abscesses caused by various organisms including Candida albicans (particularly in diabetic patients), methicillin-resistant Staphylococcus aureus, and Propionibacterium acnes, all resulting in facial nerve dysfunction 2, 5.
• The mechanism involves compression of the nerve by the abscess, especially when associated with rapid enlargement and local inflammation 6.

Critical Diagnostic Considerations

When evaluating facial palsy with parotid pathology, you must actively exclude malignancy, as facial nerve involvement classically indicates parotid malignancy rather than benign disease 7, 4.

Key distinguishing features for parotid abscess:

• Acute onset (<72 hours) of symptoms with signs of infection (fever, pain, erythema, fluctuance) 3.
• Complete ipsilateral facial weakness including forehead involvement, consistent with LMN pattern 8, 1.
• Absence of other cranial nerve deficits - multiple cranial nerve involvement suggests alternative pathology requiring immediate MRI 8, 1.
• Rapid progression - facial palsy developing within days of parotid symptoms suggests inflammatory/infectious rather than neoplastic etiology 3.

Mandatory Diagnostic Workup

• Ultrasonography or CT imaging is essential to confirm parotid abscess in any patient presenting with suppurative parotitis, particularly if facial nerve dysfunction develops 5.
• Fine needle aspiration biopsy should be performed to obtain culture data and exclude malignancy 3.
• If presentation is atypical or symptoms persist beyond 2 months, MRI with contrast is mandatory to exclude structural lesions including tumor 1.

Management Algorithm

1. Immediate treatment with intravenous antibiotics targeting likely pathogens (consider MRSA coverage in appropriate populations) 5.
2. Surgical drainage is typically required for definitive management 5.
3. Eye protection measures must be implemented immediately, including lubricating drops, ointment, and eye taping/patching to prevent permanent corneal damage 1.
4. Reassessment is mandatory if new neurologic findings develop or facial recovery is incomplete at 3 months 1.

Prognosis

• Recovery of facial nerve function is variable - some cases show complete recovery within 1-3 months with appropriate treatment 3.
• However, permanent facial nerve dysfunction can occur, particularly with delayed diagnosis or inadequate treatment 5.
• The presence of facial nerve palsy with benign parotid disease carries a better prognosis than malignancy-associated palsy, but outcomes depend on timely intervention 6.

Critical Pitfall to Avoid

Do not assume facial palsy with a parotid mass is always malignant - while malignancy remains the most common cause, benign inflammatory conditions including abscess must be considered, especially in the setting of acute infection, rapid enlargement, and appropriate risk factors (diabetes, immunosuppression) 2, 4, 6.