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Stroke Syndromes

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The Blood Supply to the Brain

The vertebral arteries and internal carotid arteries anastomose in the skull to form the Circle of Willis, which provides the blood supply to the brain. The pons and spinal cord are supplied by other branches from the vertebral arteries. Knowledge of this blood supply can help with identifying the likely area where a lesion is present in stroke.

Internal carotid arteries

The internal carotid arteries arise from the right and left common carotid arteries. They give rise to the following after passing through the cavernous sinus:

  • Ophthalmic arteries – supply the orbit
  • Posterior communicating artery – connects the Circle of Willis
  • Anterior choroidal artery
  • Anterior cerebral artery (ACA) – supplies anteromedial cerebrum

The internal carotid arteries then continue as the middle cerebral artery (MCA) which supplies the majority of the lateral part of the brain.

Vertebral arteries

The left and right vertebral arteries arise from the subclavian arteries and enter the cranial cavity via the foramen magnum and give rise to the following branches:

  • Meningeal branch
  • Anterior and posterior spinal arteries – supply the entire length of the spinal cord
  • Posterior inferior cerebellar artery (PICA)

After this, the two vertebral arteries converge to form the basilar artery, which supplies the cerebellum and pons.

The basilar artery then terminates and splits into the posterior cerebral arteries (PCA) which supply the posterior cerebrum.

Stroke Syndromes Affecting the Brain

Anterior cerebral artery syndrome

The anterior cerebral artery (ACA) supplies the anteromedial cerebrum, more specifically, the frontal, prefrontal, primary motor, and primary sensory cortices. Proximal blockages cause less severe signs and symptoms due to collateral blood flow via the anterior communicating artery.

Main features include:

  • Contralateral hemiparesis and hemisensory loss affecting the lower extremity more than the upper extremity – the most common symptom.

Middle cerebral artery syndrome

The middle cerebral artery (MCA) is the most common artery involved in stroke. It supplies the lateral part of the brain, more specifically the basal ganglia, internal capsule, and the lateral frontal, temporal, and parietal lobe.

Main features include:

  • Contralateral hemiparesis and hemisensory loss affecting the upper extremitymore than the lower extremity – the most common symptom
    • This is because the MCA supplies the lateral somatosensory cortex, which is mapped to motor and sensory functions of the face and upper extremity
  • Aphasia – since the lateral temporal and frontal lobes may be affected, where Wernicke’s and Broca’s areas are found.

Posterior cerebral artery syndrome

The posterior cerebral artery (PCA) supplies the occipital lobe and inferior temporal lobe.

Main features include:

  • Contralateral homonymous hemianopia with macular sparing
  • Visual agnosia – impaired recognition of objects presented to them despite being able to see them
  • Due to inferior occipital area lesions.

Lacunar stroke

A lacunar stroke occurs due to the occlusion of small penetrating arteries that supply deep brain structures (such as the internal capsule, basal ganglia, and thalamus). They present with pure motor or sensory loss, or ataxia with hemiparesis. Lacunar strokes may present as one of the following:

  • Hemiparesis/hemisensory loss: contralateral pure hemiparesis or hemisensory loss
  • Hemiparesis + limb ataxia: contralateral pure hemiparesis and ataxia of the contralateral limb Lacunar strokes are associated with hypertension.

Amaurosis fugax

Amaurosis fugax describes a painless temporary loss of vision in one or both eyes, classically described as a ‘black curtain coming down’.

It occurs due to occlusion of the retinal or ophthalmic artery. Other causes include giant cell arteritis and hypercoagulability.

Stroke Syndromes Affecting the Midbrain 

Midbrain  syndrome

Also known as Weber’s syndrome, midbrain syndrome is due to an occlusion of the branches of the posterior cerebral artery (PCA) that supply the midbrain. Its features include:

  • Ipsilateral CN III (oculomotor nerve) palsy:
  • Ptosis, mydriasis, and a ‘down and out’ eye
  • Contralateral hemiparesis:
  • Due to the involvement of the corticospinal tracts which decussate after the medulla.

Stroke Syndromes Affecting the Pons

Medial pontine syndrome

Medial pontine syndrome occurs due to occlusion of the paramedian branches of the basilar artery. Its features include:

  • Hemiparesis on the contralateral side of the infarct due to corticospinal tract damage
  • Ipsilateral abducens nerve damage – the eye is down and inwards towards the nose
  • There may be facial nerve involvement.

Lateral pontine syndrome

Lateral pontine syndrome occurs due to occlusion of the anterior inferior cerebellar artery. Its features include:

  • Ipsilateral upper and lower facial paralysis
  • Due to the involvement of the facial nerve nucleus
  • Ipsilateral loss of all sensation to the face
  • Due to the involvement of the trigeminal nucleus
  • Sensory deficits of the trunk and extremities contralateral to the lesion:
  • Loss of pain and temperature sensation in the trunk and extremities – spinothalamic damage (spinothalamic tracts decussate in the spinal cord)
  • Features of vestibular nuclei damage:
  • Ataxia, nystagmus, and vertigo.

Locked-in syndrome

Locked-in syndrome can occur due to an occlusion of the basilar artery.

Its features include:

  • Quadriplegia
  • Bulbar palsy – inability to speak or use the facial muscles
  • Consciousness, hearing, some eye movements, and blinking are retained

Stroke Syndromes Affecting the Medulla

Medial medullary syndrome

Medial medullary syndrome occurs due to occlusion of the anterior spinal artery leading to infarction of the medial medulla oblongata.

Its features include:

  • Hemiparesis on the contralateral side of the infarct due to corticospinal tract damage
  • Hypoglossal paralysis and tongue wasting – ipsilateral to the infarct and away from the weak arm and leg.

Lateral medullary syndrome

Lateral medullary syndrome occurs due to the occlusion of the posterior inferior cerebellar artery (PICA) leading to infarction of the lateral medulla. It is also known as Wallenberg’s syndrome.

Its features include:

  • Sensory deficits of the face ipsilateral to the lesion:
  • Loss of pain and temperature sensation in the face – trigeminal nucleus damage
  • Sensory deficits of the trunk and extremities contralateral to the lesion:
  • Loss of pain and temperature sensation in the trunk and extremities – spinothalamic damage (spinothalamic tracts decussate in the spinal cord)
  • Features of vestibular nuclei damage:
  • Ataxia, nystagmus, and vertigo.

Stroke Syndromes Affecting the Cerebellum

Cerebellar strokes can occur due to occlusion of the superior, anterior inferior, or posterior cerebellar arteries.

Features include:

Stroke Syndromes Affecting the Extracranial Arteries

Vertebrobasilar insufficiency

Narrowing or occlusion of the vertebral and basilar arteries can lead to vertebrobasilar insufficiency. Its features include:

  • Vertigo
  • Headaches
  • It may be seen in elderly patients and elicited by turning or extending the neck (temporarily occluding the arteries)

Summary of Stroke Syndromes

Syndromes affecting the brain

  • Anterior cerebral artery (ACA) syndrome:
    • Vessel and location affected: ACA, anteromedial cerebrum
    • Features:
      • Contralateral hemiparesis and sensory loss that are worse in the lower limb than in the upper limb
  • Middle cerebral artery (MCA) syndrome:
    • Vessel and location affected: MCA, lateral cerebrum
    • Features:
      • Contralateral hemiparesis and sensory loss that are worse in the upper limb than in the lower limb:
      • Due to MCA supplying lateral cortex which is mapped to sensorimotor functions of the face and upper extremity
      • Aphasia:
      • As Wernicke’s and Broca’s areas are found on the lateral cortex
  • Posterior cerebral artery (PCA) syndrome:
    • Vessel and location affected: PCA, occipital and inferior temporal lobes
    • Features:
      • Contralateral homonymous hemianopia with macular sparing
      • Visual agnosia:
        • Due to inferior occipital area lesions
  • Lacunar stroke:
    • Vessel and location affected: penetrating arteries, deep brain structures (internal capsule, basal ganglia, thalamus)
    • Features:
      • Contralateral pure hemiparesis or hemisensory loss or
      • Contralateral pure hemiparesis and contralateral ataxia
  • Amaurosis fugax:
    • Vessel and location affected: retinal or ophthalmic artery, retina
    • Features:
      • Acute painless vision loss in one or both eyes  – similar to a ‘curtain coming down’

Syndromes affecting the midbrain

  • Midbrain syndrome (Weber’s syndrome):
    • Vessel and location affected: PCA branches supplying the midbrain
    • Features:
      • Contralateral hemiparesis
      • Ipsilateral CN III palsy

Syndromes affecting the pons

  • Medial pontine syndrome:
    • Vessel and location affected: paramedian branches of basilar artery, medial pons
    • Features:
      • Contralateral hemiparesis
      • Ipsilateral CN VI palsy
  • Lateral pontine syndrome:
    • Vessel and location affected: anterior inferior cerebellar artery, lateral pons
    • Features:
      • Ipsilateral upper and lower facial paralysis
        • Due to the involvement of whole facial nerve nucleus
      • Ipsilateral loss of all sensation to the face
        • Due to the involvement of trigeminal nucleus
      • Contralateral loss of pain and temperature sensation in trunk + extremities
        • Due to spinothalamic damage (decussates in spinal cord)
      • Ataxia, nystagmus, and vertigo:
        • Due to involvement of vestibular nuclei
  • Locked-in syndrome:
    • Vessel and location affected: basilar artery, pons
    • Features:
      • Quadriplegia
      • Bulbar palsy
      • Consciousness, hearing, eye movements, and blinking retained

Syndromes affecting the medulla

  • Medial medullary syndrome:
    • Vessel and location affected: anterior spinal artery, medial medulla oblongata
    • Features:
      • Contralateral hemiparesis
      • Ipsilateral CN XII palsy – tongue deviates away from hemiparesis
  • Lateral medullary syndrome (Wallenberg’s syndrome):
    • Vessel and location affected: posterior inferior cerebellar artery, lateral medulla
    • Features:
      • Ipsilateral facial loss of pain and temperature sensation:
        • Due to trigeminal nucleus involvement
      • Contralateral trunk and extremity loss of pain and temperature sensation
        • Due to spinothalamic involvement (decussates in spinal cord)
      • Ataxia, nystagmus, and vertigo:
        • Due to vestibular nuclei involvement

Syndromes affecting the cerebellum

  • Cerebellar stroke syndrome:
    • Vessel and location affected: superior, anterior inferior, or posterior cerebellar arteries, cerebellum
    • Features:
      • Vertigo
      • Ataxia
      • Vomiting
      • Headaches

Syndromes affecting the extracranial arteries

  • Vertebrobasilar insufficiency:
    • Vessel and location affected: vertebral and basilar arteries, medulla, pons, midbrain, and cerebellum
    • Features:
      • Vertigo
      • Headaches
      • Elderly people turning or extending the neck – temporarily occludes arteries

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