Lesion Localization: Dysarthria and Ataxia
The combination of dysarthria and ataxia localizes to the basilar artery territory, specifically affecting the cerebellum (particularly the superior cerebellar artery distribution) and/or the pons. 1, 2, 3
Neuroanatomical Basis
The presentation of dysarthria combined with ataxia indicates pathology in the posterior circulation, specifically:
- Cerebellar lesions, particularly involving the dentate nuclei or superior cerebellar artery territory, cause both ataxic dysarthria and limb/truncal ataxia 1, 2
- Pontine lesions affecting the base of the pons produce dysarthria accompanied by ataxia and often pyramidal tract signs as part of an ataxic hemiparesis syndrome 2, 3
- Brainstem involvement at the pontomedullary junction can manifest with both dysarthria (from cranial nerve nuclei dysfunction) and ataxia (from cerebellar pathway disruption) 1, 3
Clinical Localization Patterns
Superior Cerebellar Artery Territory
- Dysarthria and ataxia are the predominant features when infarction affects the rostral paravermal region in the superior cerebellar artery territory 4, 2
- Isolated cerebellar infarcts causing dysarthria are consistently located in the superior cerebellar artery distribution 2
- Limb dysmetria, overshoot, and dysarthria predominate with gait ataxia being absent or transient 3
Pontine Lesions
- Lesions at the base of the pons (30.9% of dysarthria cases) produce dysarthria with accompanying ataxia and pyramidal tract signs 2
- The combination reflects involvement of both corticobulbar fibers (causing dysarthria) and cerebellar connections (causing ataxia) 3
Midbrain Involvement
- Caudal paramedian midbrain lesions involving the decussation of the superior cerebellar peduncles can produce paroxysmal dysarthria-ataxia syndrome 5
Why Not Other Arterial Territories
- Anterior cerebral artery lesions typically cause lower extremity weakness, abulia, and frontal lobe signs—not the combination of dysarthria and ataxia 6
- Middle cerebral artery lesions produce contralateral hemiparesis, hemisensory loss, and aphasia (if dominant hemisphere)—not cerebellar signs 6
- Posterior cerebral artery lesions cause visual field defects (homonymous hemianopia), alexia, and thalamic sensory symptoms—not the dysarthria-ataxia combination 6
Vascular Mechanism
- Basilar artery occlusion or branch disease is the common mechanism, with cardioembolism being the most frequent cause (52.9% of cases), followed by small-vessel disease 4, 2
- Vertebral artery dissection and artery-to-artery embolism from vertebral artery stenosis are additional mechanisms 4
Key Distinguishing Features
- The presence of ipsilateral limb dysmetria, axial lateropulsion, and ataxic dysarthria strongly suggests posterior fossa pathology in the basilar territory 4
- Associated symptoms include vertigo, headache, vomiting, and unsteadiness of gait—all consistent with posterior circulation involvement 4
- Pyramidal tract signs coexist in 90.7% of cases when dysarthria results from brainstem lesions along the pyramidal tract course 2
Answer: A. Basilar