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Facial weakness

Medicine > Neurosciences

Differential Diagnosis Schema 🧠

Upper Motor Neuron Lesions

  • Stroke: Contralateral facial weakness with sparing of the forehead, often accompanied by other neurological deficits.
  • Multiple Sclerosis: May present with facial weakness, often part of a broader neurological picture including optic neuritis or motor/sensory disturbances.
  • Brain Tumors: Gradual onset, associated with other signs of raised intracranial pressure or focal neurological deficits.
  • Trauma: Sudden onset post-head injury, often with other signs of neurological impairment.

Lower Motor Neuron Lesions

  • Bell’s Palsy: Sudden onset unilateral facial weakness, often associated with postauricular pain or altered taste.
  • Ramsay Hunt Syndrome: Facial weakness with vesicular rash in the ear canal, due to varicella-zoster virus reactivation.
  • Guillain-Barré Syndrome: Symmetric facial weakness as part of a progressive ascending paralysis.
  • Cholesteatoma: Chronic otitis media with progressive facial weakness, may be accompanied by hearing loss.
  • Sarcoidosis: Gradual onset facial weakness, possibly with other cranial nerve involvement, part of systemic disease.

Neuromuscular Junction Disorders

  • Myasthenia Gravis: Fluctuating weakness, often worsens with activity, may involve other cranial muscles.
  • Botulism: Descending paralysis starting with cranial nerves, including facial muscles, associated with pupillary abnormalities.
  • Lambert-Eaton Myasthenic Syndrome: Proximal muscle weakness, autonomic symptoms, and facilitation of weakness with exercise.

Infective Causes

  • Lyme Disease: Facial palsy, often bilateral, with history of tick exposure or erythema migrans.
  • HIV: Can cause a mononeuritis multiplex, with multiple cranial nerves potentially involved.
  • Meningitis/Encephalitis: Facial weakness with other signs of meningism or altered consciousness.
  • Otitis Media: Acute infection with spread to facial nerve causing palsy, often with ear pain and discharge.
  • Tuberculosis: Chronic meningitis can lead to cranial nerve involvement including facial palsy.

Key Points in History 🥼

Onset and Duration

  • Sudden onset: Suggests vascular causes such as stroke or Bell’s palsy.
  • Gradual onset: More likely to be a tumor or chronic inflammatory condition like multiple sclerosis.
  • Progressive weakness: Consider neurodegenerative conditions or malignancies.
  • Fluctuating weakness: Suggests myasthenia gravis.

Associated Symptoms

  • Pain: Postauricular pain is often associated with Bell’s palsy; ear pain with otitis media.
  • Rash: Vesicular rash in Ramsay Hunt syndrome; erythema migrans in Lyme disease.
  • Diplopia: Suggestive of a cranial nerve lesion involving the extraocular muscles, such as in multiple sclerosis.
  • Dysarthria: Consider central causes such as stroke or ALS.
  • Fever: Infective causes like meningitis or encephalitis.

Background

  • Past Medical History: Previous strokes, MS, or recurrent infections may suggest a recurrent or chronic cause.
  • Drug History: Recent steroid use could predispose to infection; check for neurotoxic drugs.
  • Family History: Genetic conditions like Charcot-Marie-Tooth disease or hereditary neuropathies.
  • Social History: Alcohol use, recent travel (consider infectious causes), occupation (exposure to neurotoxins).

Possible Investigations 🌡️

Blood Tests

  • Full Blood Count: To assess for infection or hematological causes of symptoms.
  • ESR/CRP: Elevated in inflammatory or infective conditions.
  • Autoantibodies: ANA, ENA, or anti-dsDNA for autoimmune conditions like lupus or Sjögren’s syndrome.
  • Lyme Serology: If there is a history suggestive of tick exposure.
  • HIV Testing: If there are risk factors or clinical suspicion of HIV.

Imaging

  • MRI Brain: To identify structural causes like tumors, MS plaques, or infarcts.
  • CT Head: Useful in acute settings to exclude hemorrhage or large infarcts.
  • Chest X-ray: May be indicated if there is suspicion of sarcoidosis or malignancy.
  • Temporal Bone CT: If cholesteatoma or other middle ear pathology is suspected.

Electrophysiology

  • Nerve Conduction Studies: To differentiate between upper and lower motor neuron lesions.
  • Electromyography (EMG): Useful in diagnosing myasthenia gravis and other neuromuscular junction disorders.
  • Evoked Potentials: May help in the diagnosis of multiple sclerosis.

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Neurosciences