Stroke Syndromes

Lacunar Syndromes

Lacunar infarctions are caused by occlusion of small, perforating cerebral vessels
- associated with typical vascular risk factors, especially hypertension
- small, perforating vessels become gradually occluded by a process called lipohyalinosis
- lacunar infarcts tend to be found within white matter regions
- the same "lacunar syndrome" may be produced by multiple different cerebral lesions
Five (or six) classically described lacunar syndromes:
- Pure motor hemiparesis
  - unilateral face/arm/leg weakness (with or without dysarthria)
  - localizations:
    - posterior limb of internal capsule (lenticulostriate arteries, anterior choroidal artery, PCA perforators)
    - ventral pons (perforating branches of basilar artery)
    - corona radiata (small MCA branches)
    - cerebral peduncle (small MCA branches)
- Dysarthria hemiparesis ("dysarthria/clumsy hand syndrome")
  - dysarthria with hand weakness/clumsiness
  - localizations:
    - same as for pure motor hemiparesis
    - posterior limb of internal capsule (lenticulostriate arteries, anterior choroidal artery, PCA perforators)
    - ventral pons (perforating branches of basilar artery)
    - corona radiata (small MCA branches)
    - cerebral peduncle (small MCA branches)
- Ataxic hemiparesis
  - unilateral face/arm/leg weakness, with limb clumsiness/ataxia
  - the ataxia is "out of keeping" with the weakness - e.g. the limb ataxia is more than would be expected for the amount of weakness
  - localizations:
    - same as for pure motor hemiparesis
    - posterior limb of internal capsule (lenticulostriate arteries, anterior choroidal artery, PCA perforators)
    - ventral pons (perforating branches of basilar artery)
    - corona radiata (small MCA branches)
    - cerebral peduncle (small MCA branches)
- Pure sensory syndrome
  - contralateral loss of all primary sensory modalities
  - localization:
    - ventral posterior lateral (VPL) nucleus of the thalamus (thalamoperforator branches of the PCA)
- Sensorimotor stroke
  - unilateral face/arm/leg weakness (with or without dysarthria)
  - contralateral loss of all primary sensory modalities
  - localization:
    - posterior limb of the internal capsule and thalamic VPL or thalamic somatosensory radiations (thalamoperforator branches of the PCA, or lenticulostriate arteries)
- Basal ganglia lacune
  - often asymptomatic, but may cause hemiballismus
  - localization:
    - caudate nucleus, putamen, globus pallidus, or subthalamic nucleus (lenticulostriate, anterior choroidal, thalamoperforator, or Heubner's arteries)

Brainstem Syndromes

There are more than 25 named brainstem stroke syndromes
- many are rare
- descriptions in clinical literature may be inconsistent
- many were described before the MRI era
- some of them might not exist...
- ... in a study of 245 patients with MRI-confirmed brainstem strokes, only 19 had a "classic" brainstem stroke syndrome (14 of those were Wallenberg) - Marx, J. J., & Thömke, F. (2009). J of Neurology, 256(6), 898–903.
Brainstem lesions classically produce "crossed deficits"
- unilateral cranial nerve deficits with contralateral motor/sensory deficits ("long tract signs")
- typical signs/symptoms of brainstem ischemia: (table)
  - nystagmus
  - ptosis
  - diplopia
  - dysarthria
  - dysphagia
  - ataxia
  - contralateral motor/sensory deficits
  - isolated dizziness is rarely due to brainstem ischemia
A few brainstem syndromes worth knowing:
- Weber syndrome
  - CN III palsy and contralateral hemiparesis
  - midbrain lesion of cerebral peduncle and CN III fascicles (figure 1) (figure 2)
- Millard-Gubler syndrome
  - CN VI and VII palsy and contralateral hemiparesis
  - pontine lesion (anterior paramedial pons) affecting CN VI and VII nucleus/fascicles, and corticospinal tracts (figure 1) (figure 2)
- Wallenberg (lateral medullary) syndrome
  - the classic! worth knowing, as it is probably the most common "named" brainstem syndrome
  - lateral medullary lesion, affecting producing... (figure 1) (figure 2)
    - ipsilateral facial pain and numbness - spinal trigeminal nucleus
    - contralateral hemibody sensory loss - spinothalamic tract
    - ispilateral clumsiness (hemiataxia), gait ataxia with lateralpulsion - spinocerebellar tract
    - oscillopsia, vertigo, nausea, and vomiting - vestibular nuclei
    - loss of taste sensation - nucleus of the tractus solitarus (NTS)
    - dysphagia, diminished gag, hoarseness - CN IX and X fibres, NTS
    - Horner syndrome - descending sympathetic tract (hypothalmospinal fibres)
...the reason to learn brainstem syndromes is to understand neuroanatomy, not because they are commonly encountered in clinical practice!

Cases

Hohol, M.J. The Neurologic Exam. Accessed at: http://neuroexam.med.utoronto.ca/main.htm