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)
CLINICAL CASES
Neurological Mind-boggler
Leave a Reply