Correct Answer: A. Superior cerebellar
Ataxia and incoordination are cardinal signs of cerebellar dysfunction. The superior cerebellar artery (SCA) is the primary arterial supply to the cerebellum, perfusing the superior and lateral portions of the cerebellar hemispheres, the dentate nucleus, and the superior cerebellar peduncle—all critical for motor coordination and balance. Thrombosis of the SCA results in acute cerebellar infarction, presenting with classic ataxia, dysmetria, dysdiadochokinesia, and gait disturbance. This is the most direct and clinically relevant answer. The SCA arises from the proximal basilar artery and is particularly vulnerable to thrombosis in patients with vertebrobasilar insufficiency, a common presentation in Indian populations with hypertension and atherosclerosis. Cerebellar stroke is a neurosurgical emergency requiring urgent imaging (CT/MRI) and may necessitate decompression if edema develops. The clinical syndrome of SCA territory infarction is well-documented in Harrison and Indian neurology texts as a classic presentation of acute cerebellar stroke.
Why the other options are wrong
B. Internal carotid — The internal carotid artery supplies the cerebral hemispheres (anterior and middle cerebral territories), not the cerebellum. Thrombosis causes contralateral hemiparesis, hemisensory loss, and aphasia/neglect—not ataxia. This is a distractor that tests knowledge of vascular territories and is a common NBE trap pairing a major artery with wrong neurological signs. C. Posterior cerebral — The PCA supplies the occipital and temporal lobes, causing visual field defects, memory loss, and thalamic syndromes—not cerebellar ataxia. While the PCA does arise from the basilar artery (like SCA), it does not supply cerebellar structures. This trap exploits confusion between posterior circulation arteries. D. Middle cerebral — The MCA is the largest cerebral artery, supplying the motor and sensory cortex, causing contralateral weakness and sensory loss—not ataxia. MCA occlusion produces focal cortical deficits, not cerebellar signs. This distractor tests whether students confuse cerebral stroke syndromes with cerebellar pathology.
High-Yield Facts
- Superior cerebellar artery (SCA) is the primary blood supply to the cerebellum, arising from the proximal basilar artery.
- SCA territory infarction presents with acute ataxia, dysmetria, dysdiadochokinesia, nystagmus, and gait disturbance—classic cerebellar syndrome.
- Vertebrobasilar insufficiency is a common cause of SCA thrombosis in Indian patients with hypertension, diabetes, and atherosclerosis.
- Cerebellar stroke is a neurosurgical emergency; mass effect from edema can cause obstructive hydrocephalus and brainstem compression requiring urgent decompression.
- The three cerebellar arteries are SCA (superior), AICA (anteroinferior), and PICA (posteroinferior); SCA occlusion is the most common cause of acute cerebellar infarction.
Mnemonics
CEREBELLUM ARTERIES (3 A's) SCA = Superior, AICA = Anteroinferior, PICA = Posteroinferior. SCA thrombosis → ataxia (remember: SCA = Cerebellar Ataxia). Use when recalling which artery causes which cerebellar syndrome. CEREBELLAR STROKE SIGNS DANISH: Dysmetria, Ataxia, Nystagmus, Intention tremor, Scanning speech, Hypotonia. All point to cerebellar pathology. Use to confirm cerebellar origin of symptoms before naming the artery.
NBE Trap
NBE pairs "ataxia" with major cerebral arteries (ICA, MCA, PCA) to test whether students reflexively choose large arteries or correctly identify the cerebellar circulation. The trap exploits confusion between cerebral stroke syndromes (hemiparesis, aphasia) and cerebellar syndromes (ataxia, incoordination).
Clinical Pearl
In Indian emergency departments, acute cerebellar stroke is often missed because patients present with "dizziness" and ataxia, mimicking vestibular disease. Urgent MRI and SCA territory recognition are critical—delayed diagnosis risks herniation and death. Always ask: "Is this vertigo (vestibular) or ataxia (cerebellar)?" and image accordingly.
_Reference: Harrison Ch. 445 (Cerebrovascular Diseases); Robbins Ch. 28 (Nervous System); Indian Neurology texts (Dastur & Iyer on Stroke)_