Why Posterior Cerebellar Artery Stroke Spares Vertical Gaze and Blinking
Posterior cerebellar artery (PCA) stroke spares vertical gaze and blinking because these functions are controlled by neural structures in the midbrain that are not supplied by the posterior cerebellar circulation. 1, 2
Anatomical Basis for Preserved Functions
- Vertical gaze movements are primarily controlled by the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and the interstitial nucleus of Cajal (INC) located in the midbrain, which receive blood supply from the posterior cerebral artery and not the posterior cerebellar artery 2, 3
- The posterior cerebellar artery (specifically the posterior inferior cerebellar artery or PICA) supplies the inferior cerebellum including the lobulus semilunaris inferior, lobulus gracilis, lobulus biventer, tonsilla cerebelli, and in the vermis: the clivus, tuber, pyramis, uvula and nodulus 4
- PICA territory does not include the midbrain structures responsible for vertical eye movements, which explains why vertical gaze remains intact 4
- Blinking is controlled by facial nerve nuclei in the pons and the orbicularis oculi muscles, which are not primarily supplied by the posterior cerebellar artery 1
Clinical Manifestations of Posterior Cerebellar Artery Stroke
- Posterior cerebellar artery strokes typically present with a triad of vertigo, headache, and gait imbalance, rather than eye movement disorders 5
- Common symptoms include nausea, vomiting, dizziness, and ataxia, but vertical gaze palsy is notably absent 1
- Physical examination may reveal nystagmus (often horizontal rather than vertical), truncal ataxia, and limb coordination deficits 6, 5
- Hearing loss is common with anterior inferior cerebellar artery infarction, while intractable hiccups may be seen in posterior inferior cerebellar artery infarction 1
Contrast with Midbrain Strokes
- Midbrain infarctions, particularly those affecting the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), can cause bidirectional vertical gaze palsy 2
- A unilateral midbrain lesion involving the riMLF and INC can cause complete bidirectional vertical gaze palsy by interrupting pathways just before they decussate 2
- Top of the basilar syndrome, which affects midbrain structures, includes vertical gaze paralysis among its symptoms 1
- Impaired downgaze is particularly associated with rostral midbrain infarction 3
Clinical Significance
- Understanding the preservation of vertical gaze and blinking in posterior cerebellar artery strokes helps in localizing the lesion during neurological examination 1
- The National Institutes of Health Stroke Scale (NIHSS) may underestimate the severity of posterior circulation strokes as it focuses more on limb and speech impairments rather than cranial nerve lesions 1
- Posterior circulation strokes can be difficult to diagnose due to non-specific symptoms, making the preservation of certain neurological functions like vertical gaze important diagnostic clues 1, 7
- Cerebellar infarcts in the posterior inferior cerebellar artery distribution have distinct differences in clinical presentation compared to other vascular territories, with specific patterns of preserved and impaired functions 5
Understanding these anatomical relationships is crucial for accurate diagnosis and appropriate management of posterior circulation strokes.