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This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Forehead-sparing facial weakness suggests an upper motor neuron lesion and should trigger stroke assessment.
- Complete unilateral facial weakness including forehead, hyperacusis, taste change and dry eye favours Bell palsy only after red flags are excluded.
- Multiple cranial nerve palsies, headache, fever, cancer, immunosuppression or papilloedema are not Bell palsy.
- Diplopia localises by ocular motor nerve pattern and may signal aneurysm, cavernous sinus disease, microvascular palsy, myasthenia or brainstem stroke.
- Eye protection is essential in lower motor neuron facial palsy with incomplete eye closure.
Approach to the Presentation
Localise first. Determine whether facial weakness is upper motor neuron (forehead spared, often limb/speech signs) or lower motor neuron (entire half of face). For diplopia or other cranial neuropathies, identify the nerve(s), pupil involvement, pain, trauma, vascular risk, diabetes, infection, rash and cancer history.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Stroke / brainstem stroke | must-not-miss | Forehead-sparing facial weakness, dysarthria, limb weakness/numbness, ataxia, gaze palsy or crossed findings | CT/CTA stroke pathway; MRI if posterior/brainstem concern |
| Cavernous sinus syndrome | must-not-miss | Painful ophthalmoplegia, V1/V2 sensory loss, proptosis/chemosis; thrombosis, tumour or infection | MRI/MRV/CTV cavernous sinus |
| Posterior communicating artery aneurysm causing CN III palsy | must-not-miss | Painful third nerve palsy with pupil involvement, ptosis, eye down-and-out | Urgent CTA/MRA |
| Meningitis / basal skull process | must-not-miss | Multiple cranial neuropathies, fever, meningism, cancer or TB risk | MRI/LP after safety assessment |
| Bell palsy | common | Acute unilateral LMN facial weakness including forehead, ear pain, hyperacusis, taste/lacrimation changes, no other neuro deficits | Clinical diagnosis after excluding red flags |
| Microvascular ocular motor palsy | common | Older diabetic/vascular risk, isolated pupil-sparing III, IV or VI palsy | Clinical plus risk assessment; image if atypical |
| Ramsay Hunt syndrome | less common | LMN facial palsy with ear pain and vesicles in ear/palate; hearing/vestibular symptoms | Clinical; VZV |
| Myasthenia gravis | less common | Variable ptosis/diplopia, fatigable, pupils normal, may have bulbar weakness | AChR/MuSK antibodies, ice pack, EMG |
| Lyme facial palsy | less common | Facial palsy in endemic area, tick exposure, erythema migrans, bilateral palsy possible | Lyme serology depending on exposure and timing |
| Acoustic neuroma / CPA lesion | less common | Progressive unilateral hearing loss/tinnitus, imbalance, facial numbness/weakness | MRI internal auditory canals |
Red Flags & Key History
Symptoms
Forehead-sparing facial droop or associated limb/speech symptoms
Painful pupil-involving third nerve palsy
Multiple cranial nerve palsies
Fever, meningism, immunosuppression or cancer history
Ear vesicles or severe otalgia
Signs
Forehead involvement
Pupil dilation with III palsy
Papilloedema
Proptosis/chemosis
Incomplete eye closure
Approach to Investigation
First-line
Full cranial nerve + limb neurological examIdentifies UMN signs, brainstem/cavernous sinus patterns and mimics.
Stroke assessment with glucose and CT/CTAFor forehead-sparing or associated deficits.
Eye examinationPupils, ocular movements, corneal exposure and visual acuity.
Second-line
MRI brain/brainstem/internal auditory canalsMultiple cranial neuropathies, progressive symptoms, hearing loss or atypical facial palsy.
CTA/MRAPainful pupil-involving third nerve palsy or aneurysm concern.
Lyme testingWhen epidemiological exposure supports.
Specialist
Neurology/ophthalmology/ENTStroke signs, ocular motor palsy, multiple nerves, Ramsay Hunt, corneal exposure or atypical Bell palsy.
Management Principles
Canadian stroke approach + MCC CVA/TIA objective1
Stroke pattern
- Activate stroke pathway for UMN facial weakness or associated neurological deficits
- Do not diagnose Bell palsy if forehead is spared or limb/speech signs are present
2
Bell palsy
- Prednisone started within 72 hours if no contraindication
- Eye lubrication, taping/patch at night if incomplete closure
- Consider antivirals in severe complete palsy or Ramsay Hunt; treat VZV when vesicles/otalgia
3
Ocular motor palsy
- Pupil-involving painful III palsy: urgent vascular imaging
- Isolated microvascular palsy requires close follow-up and risk-factor management, but image if atypical or not improving
4
Multiple cranial neuropathies
- Urgent imaging and targeted infectious, inflammatory or malignant workup
Complications & Pitfalls
- Bell palsy overdiagnosis: forehead-sparing weakness is central until proven otherwise.
- Forgetting eye protection: corneal injury is preventable.
- Missing aneurysm: painful pupil-involving third nerve palsy is an emergency.
- Ignoring multiple nerves: think cavernous sinus, meningitis or malignancy.
MCCQE1 Exam Tips
- 1UMN facial weakness spares the forehead; LMN affects the whole half-face.
- 2Bell palsy is a diagnosis after excluding stroke and red flags.
- 3Painful dilated pupil with CN III palsy = aneurysm until proven otherwise.
- 4Myasthenia causes pupils to remain normal.
- 5Ramsay Hunt has vesicles and is generally more severe than Bell palsy.
- 6Eye lubrication is a key management step in LMN facial palsy.
Put your reading into practice
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