MRI Brain Report - Clinical Interpretation

Finding 1: Acute Left Cerebellar Infarct (Inferomedial Aspect)

What the Imaging Shows

• Restricted diffusion on DWI (Diffusion Weighted Imaging) in the inferomedial left cerebellar hemisphere is the hallmark of acute ischemic infarction - cytotoxic edema restricts water diffusion within hours of onset
• Non-hemorrhagic = no blood products (no T1 hyperintensity, no susceptibility artifact), making thrombolysis or anticoagulation safer from a hemorrhagic transformation standpoint
• Inferomedial location = this is the territory of the posterior inferior cerebellar artery (PICA) or the medial branch of PICA, which arises from the intracranial vertebral artery

Vascular Anatomy and Correlation

"Blood supply to the cerebellum consists of three arteries of the vertebral-basilar system: the posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), and superior cerebellar artery. PICA (Wallenberg) syndrome involves the lateral medulla, inferior cerebellar peduncle, inferior vermis, cerebellar tonsils, and inferior cerebellar hemisphere."

Expected Clinical Presentation (PICA Syndrome)

• Acute vertigo, nausea, vomiting (most common presenting triad - present in ~70% and ~56% respectively)
• Ipsilateral limb ataxia and gait ataxia (~59% of cases)
• Dysarthria (~42%)
• Nystagmus, predominantly toward the side of the infarct
• Ipsilateral Horner syndrome (ptosis, miosis, anhidrosis) from involvement of the descending sympathetic tract
• Ipsilateral hemifacial pain/temperature loss (spinal trigeminal nucleus)
• Contralateral body pain/temperature loss (spinothalamic tract)
• Hoarseness / dysphagia if lateral medulla is co-involved (Wallenberg syndrome)

Critical Warning: Space-Occupying Risk

"Cerebellar infarction can act as a mass lesion if there is cerebellar edema... progression, if it is to occur, develops by the third day and may progress to coma within 24 hours. Progression is characterized by more intense ipsilateral dysmetria followed by increasing drowsiness leading to stupor, then miotic and poorly reactive pupils, conjugate gaze paralysis, ipsilateral peripheral facial paralysis, and extensor plantar responses."

Finding 2: Left Vertebral Artery Occlusion at Origin

Significance

"The posterior circulation is composed of the paired vertebral arteries, the basilar artery, and the paired PCAs. Occlusion of each vessel produces its own distinctive syndrome."

"Hypertension, atrial fibrillation, hypercholesterolemia, and diabetes are important risk factors in the elderly; vertebral artery dissection should be considered in younger patients."

Workup Needed

• Echocardiography + cardiac monitoring (Holter/telemetry) to exclude cardioembolic source
• Fasting lipid panel, HbA1c, BP monitoring
• If younger patient or history of neck trauma: CTA/MRA of the neck for dissection (intramural hematoma, pseudolumen)
• Right VA assessment - the contralateral VA must be evaluated for adequacy of posterior circulation (if both VAs are compromised, basilar ischemia risk is very high)

Finding 3: Chronic Bilateral Fronto-Parietal White Matter Foci (T2 Hyperintensities)

• Typically caused by chronic hypertension, diabetes, or aging causing lipohyalinosis of small penetrating arteries
• In the context of the current stroke, these lesions confirm pre-existing cerebrovascular disease and argue for aggressive secondary prevention
• They are also associated with increased risk of future cognitive decline, falls, and recurrent stroke

Finding 4: Tiny Left Supraclinoid ICA Aneurysm (2.3 x 2.2 x 1.5 mm)

Anatomy

• Supraclinoid segment of the ICA = the segment above the anterior clinoid process, after the ICA exits the cavernous sinus. This is a common location for saccular aneurysms (along with the ICA-PComm junction, MCA bifurcation, and AComm)
• Projecting medially - this projection direction is relevant for surgical planning if ever intervention is warranted
• Saccular (berry) aneurysm - the most common type (>90%), located at arterial bifurcation or branching points

Risk Assessment

"The International Study of Unruptured Intracranial Aneurysms Investigators found a low rate of rupture, approximately 0.1% yearly, for aneurysms smaller than 7 mm in diameter, an annual risk of 0.5% for aneurysms between 7 and 10 mm... Such data aids in comparing the risk of surgery and endovascular treatment, which, for example, exceeds the risk of bleeding within 5 years for small aneurysms located in the carotid circulation."

"Data indicate that there is no benefit from treating aneurysms of the anterior circulation that are 7 mm or less in diameter, regardless of the patient's age, if there is no prior history of SAH."

• Conservative management / observation
• Follow-up MRA (typically at 6-12 months, then annually for 2-3 years if stable)
• Risk factor control: smoking cessation (smoking significantly increases rupture risk), blood pressure management
• No intervention warranted unless it grows, changes morphology, or the patient develops symptoms

Summary Table

Key Clinical Priorities

1. Acute stroke management - admission to a stroke unit, BP management (permissive hypertension initially, target <180/105 mmHg acutely), antiplatelet therapy (aspirin 300 mg loading, then 75-100 mg daily), statin therapy
2. Monitor for malignant cerebellar edema - serial neuro checks, low threshold for repeat imaging, neurosurgical team on standby
3. Etiology workup - cardiac monitoring, echocardiogram, vascular imaging of the neck and right vertebral artery
4. Secondary prevention - antiplatelet agents (or anticoagulation if cardioembolic), statin, antihypertensives
5. Aneurysm surveillance - MRA at 6-12 months; no immediate intervention needed for a 2.3 mm aneurysm