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Home | LITFL | Clinical Cases | Brainstem lesions

Brainstem lesions

by Dr Chris Nickson, last update March 28, 2019

aka Neurological Mind-boggler 003

Here are some scenarios to try out Gates’ Brainstem Rules of 4 (original figures and re-imagined images)


Scenario 1

You are examining a patient with sudden onset left-sided weakness. These are your clinical examination findings:

  • weakness of the left upper and lower limbs, with sparing of the face.
  • tongue deviation to the right, with no ophthalmoplegia.
  • loss of vibration and proprioception in the left upper and lower limbs.

Questions

Where is the lesion?

Answer and interpretation
  • weakness of the left upper and lower limbs, with sparing of the face:
    • motor (corticospinal pathway) localises the lesion to the contralateral medial brainstem
    • (sparing of the face (CN7) means the lesion must be below the upper pons)
  • tongue deviation to the right, with no ophthalmoplegia:
    • tongue deviation indicates CN12 involvement, localising the lesion to the ipsilateral medulla
    • (sparing of CN3 and CN6 means the midbrain and pons are not involved)
  • loss of vibration and proprioception in the left upper and lower limbs:
    • confirms localisation of the lesion to the contralateral medial brainstem

Site of the lesion: right medial medulla.

Sometimes, due to the peculiar pattern of blood supply to the medulla, bilateral infarction may occur.


Scenario 2

You are examining a patient with sudden onset right-sided weakness. These are your clinical examination findings:

  • weakness of the right face, upper and lower limbs.
  • the left eye is turned “down and out” and the pupil is dilated.

Where is the lesion?

Answer and interpretation
  • weakness of the right face, upper and lower limbs:
    • motor (corticospinal pathway) localises the lesion to the contralateral medial brainste
    • (involvement of the face means the lesion must be at or above the upper pons)
  • the left eye is turned “down and out” and the pupil is dilated:
    • CN3 involvement, localising the lesion to the ipsilateral midbrain
    • (sparing of CN6 and CN12 means the pons and medulla are not involved)

Site of the lesion: left medial midbrain.

A CN3 palsy (from damage to the CN3 nerve fascicle) and contralateral hemiplegia is known as Weber syndrome (“basal” infarction) – which can be difficult to distinguish from ‘coning’ if you don’t have a CT scanner available.


Scenario 3

You are examining a patient with vertigo, vomiting, and nystagmus. These are your clinical examination findings:

  • left-sided limb ataxia.
  • left-sided alteration of pain and temperature on the face.
  • left-sided ipsilateral Homer’s syndrome.
  • right-sided alteration of pain and temperature affecting the arm and leg.
  • dysarthria and decreased gag reflex on the left, with the palate pulling up on the right-side

Where is the lesion?

Answer and interpretation
  • left-sided limb ataxia:
    spinocerebellar pathway localises the lesion to the ipsilateral lateral brainstem.
  • left-sided alteration of pain and temperature on the face:
    Sensory nucleus of the 5th cranial nerve localises the lesion to the ipsilateral lateral brainstem.
  • left-sided ipsilateral Homer’s syndrome:Sympathetic pathway localises the lesion to the ipsilateral lateral brainstem.
  • right-sided alteration of pain and temperature affecting the arm and leg:
    Spinothalamic pathway localises the lesion to the contralateral lateral brainstem.
  • dysarthria and decreased gag reflex on the left, with the palate pulling up on the right-side:
    localises the lesion to the medulla affecting the ipsilateral CN9 and 10.

Site of the lesion: left lateral medulla.

Also known as Wallenberg syndrome, caused by a left vertebral or left posterior inferior cerebellar artery occlusion (blood supply is variable to this region).


Scenario 4

You are examining a patient with right-sided deafness, that was preceded by tinnitus. These are your clinical examination findings:

  • right-sided limb ataxia (predominantly affecting the right upper limb).
  • right-sided facial numbness with loss of the corneal reflex.
  • right-sided hemi-facial spasms.

Where is the lesion?

Answer and interpretation
  • right-sided limb ataxia (predominantly affecting the right upper limb):
    • spinocerebellar pathway localises the lesion to the ipsilateral lateral brainstem.
  • right-sided facial numbness with loss of the corneal reflex:
    • Sensory nucleus of the 5th cranial nerve localises the lesion to the ipsilateral lateral brainstem.
  • right-sided hemi-facial spasms:
    • the lesion involves the pons affecting the ipsilateral CN7.

Site of the lesion: The findings indicate a lesion affecting the right lateral pons with evidence of spinocerebellar involvement.

In this case the lesion was not vascular in origin but in fact an example of a cerebellopontine angle lesion – an acoustic neuroma (or schwannoma). This demonstrates the broader utility of Gates’ Brainstem Rules of 4


References
  • Gates P. The rule of 4 of the brainstem: a simplified method for understanding brainstem anatomy and brainstem vascular syndromes for the non-neurologist. Internal Medicine Journal 2005; 35: 263-266 [PMID 15836511]
  • Goldberg S. Clinical Neuroanatomy Made Ridiculously Simple. MedMaster Series, 2000 Edition.
  • Patten J. Neurological Differential Diagnosis. Springer-Verlag.
  • Brainstem Rules of 4 (original rules)
  • Helpful Brainstem Figures (original figures)
  • The rule of 4 of the brainstem (Rules re-imagined)
  • A spider called Willis
  • Using the Brainstem 1
  • Using the Brainstem 2
  • The Magic of the Neuro Exam
  • Look Left, Look Right (Internuclear Ophthalmoplegia)
  • More Befuddling Pupillary Asymmetry (Horner Syndrome)

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About Dr Chris Nickson

An oslerphile emergency physician and intensivist suffering from a bad case of knowledge dipsosis. Key areas of interest include: the ED-ICU interface, toxicology, simulation and the free open-access meducation (FOAM) revolution. @Twitter | INTENSIVE| SMACC

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