Step 1 of 10
Central vs Peripheral Triage
Forehead spared (UMN/stroke) vs whole hemiface (LMN/facial nerve)
The opening decision in any facial weakness is anatomic, not aetiological. The forehead receives bilateral cortical input, so an upper-motor-neuron (central) lesion spares the forehead and weakens only the contralateral lower face. A lower-motor-neuron (peripheral) lesion involves the entire hemiface — brow, eye closure, and mouth together. This single observation separates a stroke pathway from the facial-nerve algorithm.
Central weakness rarely travels alone. Limb weakness, aphasia, ataxia, dysarthria, or a gaze deviation alongside facial droop point to a cerebral or brainstem event and mandate the acute stroke pathway — urgent CT/MRI brain, vascular imaging, and neurology referral — not an otologic workup. Only once the weakness is confirmed peripheral does the patient enter the remainder of this algorithm.
- Forehead spared + lower-face weakness + other neurological deficits → central (UMN) → stroke pathway
- Whole hemiface weak (brow, eye, mouth) with incomplete eye closure → peripheral (LMN) → continue
- Screen for limb weakness, aphasia, ataxia, dysarthria, gaze deviation at first contact
- When uncertain, treat as central and image the brain — a missed stroke is the costlier error
★ High-yield pearls (chapter-wide)
- All that palsies is not Bell's palsy — Bell's is a diagnosis of exclusion, not a label of convenience. A spared forehead, a slowly progressive course, or recurrence on the same side each overturns it.
- Eye protection is the first intervention in every patient who cannot fully close the eye — exposure keratopathy can blind faster than the palsy resolves.
- Forehead sparing means central until proven otherwise — a stroke pathway, not a facial-nerve pathway.
- Paralysis that is progressive beyond three weeks is a tumour until proven otherwise — image the whole nerve from brainstem to parotid.
- Recurrent ipsilateral palsy mandates imaging — facial nerve schwannoma, haemangioma, or perineural malignant spread hide behind a 'recurrent Bell's' label.
- Start prednisolone within 72 hours of onset in Bell's palsy — the evidence-based window is narrow and recovery hinges on it.
- Vesicles in the ear canal, concha, or palate with severe otalgia define Ramsay Hunt — outcomes are worse than Bell's and demand combined steroid-antiviral therapy.
- Electroneurography between day 3 and day 14 stratifies prognosis in complete palsy — greater than 90% degeneration is the surgical-decompression threshold.
- No recovery at six months reopens the workup — repeat contrast MRI and consider PET-CT before accepting an idiopathic diagnosis.
Evidence base
3 sources- HIGH
Hohman MH & Hadlock TA · Laryngoscope · 2014Large case seriesPMID 24431233
Large modern series defining the etiologic distribution of facial paralysis and supporting the diagnostic evaluation.
- HIGHFacial Nerve Disorders and Diseases: Diagnosis and Management
Guntinas-Lichius O & Schaitkin BM · Thieme · 2016Textbook
Comprehensive contemporary textbook covering the diagnosis, imaging, grading, and management of facial nerve disorders.
- HIGHThe Facial Nerve
May M & Schaitkin BM · Thieme · 2000Textbook
Classic reference from which many modern facial paralysis algorithms derive.
Decision tree
The triage screen is the first gate. Classification routes the stable patient to one of the aetiology-keyed pathways below. Cross-cut cards capture the chapter's must-not-miss rules.