6. Stroke 2- Brainstem Syndromes

What are the three levels of the brainstem from top to bottom?

Midbrain, pons, medulla.

What is the function of the reticular activating system?

Maintains consciousness.

Where is the reticular activating system located?

Posterior brainstem from midbrain to medulla.

Where are cranial nerve nuclei located in the brainstem?

On the same (ipsilateral) side as their cranial nerve.

Where do descending corticobulbar fibers come from?

The contralateral cortex.

What is the medial longitudinal fasciculus (MLF) responsible for?

Coordinating horizontal eye movements between CN6 and CN3.

Where do corticospinal tracts decussate?

At the base of the medulla.

What are the pyramids in the brainstem?

Corticospinal and corticobulbar tracts bundled together.

What sensation is carried by the spinothalamic tract?

Pain and temperature.

Where does the spinothalamic tract run in the brainstem?

Laterally.

Where does the spinothalamic tract cross?

In the spinal cord before reaching the brainstem.

What sensation is carried by the dorsal column-medial lemniscus pathway?

Vibration and proprioception.

Where do dorsal columns decussate?

At the base of the medulla.

What is the medial lemniscus?

The dorsal column pathway after it crosses in the medulla.

What are crossed findings in brainstem lesions?

CN deficits on one side with opposite-sided body motor/sensory deficits.

Why do brainstem lesions produce crossed findings?

Because most are above the motor and sensory decussations in the medulla.

What is the Gates Rule of 4 used for?

Localizing brainstem lesions.

Which cranial nerves come from the midbrain?

CN 3 and CN 4.

Which cranial nerves come from the pons?

CN 6, 7, and 8.

Which cranial nerves come from the medulla?

CN 9, 10, 11, and 12.

Which cranial nerves do NOT have nuclei in the brainstem?

CN 1 and CN 2.

Which cranial nerve is not useful for localization due to broad distribution?

CN 5.

What type of function do medial brainstem structures generally have?

Mostly motor.

Which tracts and nuclei are found in the medial brainstem?

Corticospinal tract, CN 3/4/6/12 nuclei, MLF, medial lemniscus.

What does the medial longitudinal fasciculus do?

Coordinates horizontal eye movements between CN6 and CN3.

What sensory pathway is in the medial brainstem despite starting with 'M'?

Medial lemniscus (proprioception/vibration).

What type of function do lateral brainstem structures generally have?

Mostly sensory.

Which structures are found in the lateral brainstem?

Spinothalamic tract, trigeminal sensory nucleus, spinocerebellar tract, sympathetic tract.

Which cranial nerve nuclei are found medially?

CN 3, 4, 6, and 12 (divide evenly into 12).

Which cranial nerve nuclei are found laterally?

CN 5, 7, 9, and 11 (do not divide evenly into 12).

What artery is typically involved in lateral medullary syndrome?

Posterior inferior cerebellar artery (PICA).

What are classic symptoms of lateral medullary syndrome?

Dysphagia, hoarseness, vertigo, nystagmus, loss of pain/temp on ipsilateral face and contralateral body.

What brainstem stroke presents with crossed pain/temp loss and swallowing deficits?

Lateral medullary syndrome.

What structure causes ipsilateral facial pain/temp loss in lateral medullary syndrome?

Spinal trigeminal nucleus and tract.

What structure causes contralateral body pain/temp loss in lateral medullary syndrome?

Spinothalamic tract.

What structure causes vertigo and nystagmus in lateral medullary syndrome?

Vestibular nuclei.

What structure causes dysphagia and hoarseness in lateral medullary syndrome?

Nucleus ambiguus.

What structure causes ipsilateral ataxia in lateral medullary syndrome?

Inferior cerebellar peduncle.

What structure causes ipsilateral Horner’s syndrome in lateral medullary syndrome?

Disruption of descending sympathetic fibers.

What artery is typically involved in ventral pontine stroke?

Paramedian branches of the basilar artery.

What are classic symptoms of ventral pontine stroke?

Contralateral hemiparesis, dysarthria, and ipsilateral facial weakness.

What structure causes contralateral weakness in ventral pontine stroke?

Corticospinal tract.

What structure causes dysarthria in ventral pontine stroke?

Corticobulbar tract.

What structure causes ipsilateral facial weakness in ventral pontine stroke?

Facial nerve fascicle (CN VII).

What is the name of the classic ventral pontine stroke syndrome?

Millard-Gubler syndrome.

What arteries are typically involved in midbrain strokes?

Branches of the posterior cerebral artery (PCA).

What are classic symptoms of midbrain stroke?

Ipsilateral CN III palsy and contralateral hemiparesis.

What is the name of the classic midbrain stroke syndrome?

Weber syndrome.

What structure causes ipsilateral eye movement deficits in midbrain stroke?

CN III fascicle.

What structure causes contralateral body weakness in midbrain stroke?

Cerebral peduncle (corticospinal tract).