Neuroimaging Case Review: Cases 1-5

Case 1: Acute presentation of stroke symptoms in a 72-year-old male

• Presentation and context
  • Acute onset of contralateral sensory loss and right arm weakness.
  • Aligns with signs of stroke on the Bates table: contralateral face/arm sensory/motor findings; potential aphasia, apraxia, neglect depending on lesion location.
  • The instructor emphasizes case-by-case imaging review and interactive Q&A; focus on understanding imaging findings and why they appear.
• Key diagnostic questions and workflow
  • Diagnosis categories commonly asked: (a) most likely diagnosis, (b) next step to evaluate, (c) imaging, (d) treatment considerations, (e) risk factors in history and physical exam findings for stroke.
  • First-line imaging in this vignette: non-contrast CT (NCCT) of the head to rapidly assess for hemorrhage.
  • Rationale for NCCT first: fast, readily available in emergency settings, and excellent for quickly ruling in/out bleed to determine eligibility for thrombolysis.
  • If no hemorrhage is seen on NCCT, consider further imaging to characterize ischemia (MRI with DWI, CT perfusion, CT angiography). Lumbar puncture is discussed as a potential option if subarachnoid hemorrhage is suspected and CT is negative in the appropriate era.
• Imaging findings and concepts
  • Non-contrast CT (NCCT) findings in acute ischemia can show a hyperdense vessel or wedge-shaped/web-shaped hyperdensity indicating vascular pathology or early infarct changes.
  • Figure reference: Arrow points to MCA; interpretation suggested as thrombotic MCA with acute ischemic infarct pattern.
  • Ischemic infarct evolution on CT/MRI (concepts introduced, not all times shown):
  • NCCT: early ischemia may be subtle; loss of gray-white differentiation can occur with edema.
  • MRI (DWI): acute infarct appears bright due to restricted diffusion; diffusion restriction confirmed by ADC decrease.
  • MRI limitations: longer exam time, availability, contraindications (pacemakers, intraocular metallic foreign bodies).
  • MRI role: DWI (diffusion-weighted imaging) is highly sensitive for acute infarction within minutes; ADC (apparent diffusion coefficient) decrease confirms restricted diffusion.
  • Other imaging modalities discussed:
  • CT angiography (CTA) or CT perfusion (CTP) to assess vessel status and penumbra.
  • MR angiography (MRA) as an alternative to CTA.
  • Digital subtraction angiography (DSA) described as the gold standard for detailed vascular anatomy when planning intervention.
• Practical imaging notes and implications
  • Hyperdensity on CT = blood/hemorrhage is “bright” or hyperdense; the term used is hyperdense for white on CT.
  • If hemorrhage is not seen on NCCT, MRI can be performed to better identify acute ischemia.
  • Remember that CT is primarily to exclude hemorrhage, not to diagnose acute ischemia; MRI is more sensitive for acute infarct detection.
• Summary takeaways for Case 1
  • Immediate NCCT to exclude bleed is standard in suspected stroke.
  • If NCCT is negative for hemorrhage, pursue MRI with DWI to confirm acute infarct; consider CTA/MRA to assess vessel status and perfusion imaging to evaluate penumbra.
  • Be mindful of MRI contraindications and availability.
  • Clinical signs such as contralateral face/arm weakness guide localization (often MCA territory).

Case 2: 59-year-old hypertensive male with headache and acute sensory deficit

• Presentation and context
  • Hypertensive male presenting with headache and acute sensory deficit; discussion highlights broad differential diagnoses in hypertensive patients with acute neuro symptoms.
  • Emphasis on risk factor implications: chronic hypertension weakens small brain vessels, increasing risk of hemorrhagic stroke, especially in deep structures like basal ganglia and thalamus.
• Imaging approach and reasoning
  • Initial imaging: NCCT to assess for spontaneous intracranial hemorrhage (bleed). In hypertensive patients, think about hemorrhage risk and location (deep structures: basal ganglia, thalamus, brainstem, or cerebellum).
  • If NCCT shows a hyperdense lesion, consider whether it represents acute hemorrhage; microbleeds may be present as small dark spots on other sequences.
  • MRI role and time course of hemorrhage evolution (conceptual, not a single image):
  • Hyperacute (hours): blood as fresh; on some sequences, may appear darker than normal on T1; early changes reflect oxygenation status.
  • Acute (0–hours to days): deoxyhemoglobin present; imaging may appear dark on T2 and T1 in some sequences.
  • Subacute (days to weeks): methemoglobin formation; lesion becomes hyperintense (bright) on T1 and T2.
  • Chronic (weeks to months): hemosiderin/iron deposition; dark on T2 (and often T1) due to iron.
  • The case discussion notes the possibility of old microbleeds appearing within larger lesions (chronic microbleeds).
  • Imaging views: axial NCCT shows hyperdense acute bleed; sagittal MRI at times shows subacute/chronic changes and helps differentiate acute vs chronic hemorrhage.
• Practical concepts and implications
  • CT limitations: hemorrhage may be subtle; MRI provides greater sensitivity for hemorrhagic and ischemic pathology but has contraindications and availability concerns.
  • Additional imaging considerations: CT perfusion and CTA/ MRA can be used to evaluate perfusion and vessel status when considering thrombolysis or endovascular therapy.
  • The case emphasizes arterial/venous disease understanding and how chronic hypertension contributes to vascular vulnerability.
• Summary takeaways for Case 2
  • In hypertensive patients with acute neuro symptoms, NCCT is first-line to assess for bleed; if negative and clinical suspicion for ischemia remains, pursue MRI with DWI/ADC and consider perfusion imaging and vessel imaging (CTA/MRA).
  • Distinguish acute vs subacute vs chronic hemorrhage on MRI using sequence changes and iron deposition patterns; microbleeds can influence prognosis and management.

Case 3: Traumatic intracranial extra-axial hemorrhage after head injury

• Presentation and context
  • Patient presents after head trauma with signs suggesting traumatic intracranial bleeding.
  • Term “extra-axial hemorrhage” is used to denote bleeding on the surface of the brain (outside the brain parenchyma).
• Imaging approach and key findings
  • NCCT is the initial, rapid imaging modality in trauma.
  • Epidural hematoma (EDH): biconvex (lens-shaped)/hockey-helmet shape; does not cross sutures due to dural attachment to skull; commonly associated with temporoparietal region; often linked to middle meningeal artery injury and cranial fracture.
  • Subdural hematoma (SDH): crescent-shaped (banana-shaped) crescent figure that can cross suture lines but typically does not cross the midline; can result from high-energy trauma or minor head injury in elderly or anticoagulated patients.
  • Subarachnoid hemorrhage (SAH): blood within the subarachnoid and subpial spaces; can appear as star-shaped or basal patterns along CSF spaces; may necessitate MRI or lumbar puncture if CT is negative and suspicion remains.
• Additional considerations and variants
  • EDH frequently results from calvarial fracture and middle meningeal artery injury.
  • SDH more likely to occur with severe head injury or in patients using anticoagulants; can also be seen in chronic subdural bleeds.
  • SAH in trauma can be from vascular injuries or aneurysms; MRI can help, and lumbar puncture may be used if CT is negative but suspicion remains.
• Case-specific notes
  • Emphasis on quantifying shape and location on CT: EDH (convex, does not cross sutures), SDH (crescent, may cross sutures but not midline), SAH pattern in CSF spaces.
  • The role of CT to rapidly identify the bleed type and guide emergent management decisions; recognition of patterns helps differentiate etiologies.
• Summary takeaways for Case 3
  • In traumatic injury with suspected bleed, NCCT is first-line to identify EDH, SDH, or SAH.
  • Correctly identifying shape and suture crossing properties helps differentiate EDH vs SDH vs SAH.
  • CT angiography and MRI can further characterize vascular injuries if needed; the overall management hinges on precise bleed type and location.

Case 4: Unconscious patient with normal non-contrast CT – Diffuse axonal injury (DAI)

• Presentation and context
  • Unconscious patient with a normal NCCT.
  • Clinical suspicion points toward diffuse axonal injury (DAI), a severe traumatic brain injury process not necessarily visible on initial CT.
• Pathophysiology and mechanism
  • DAI results from twisting or shearing forces within the brain during rapid acceleration/deceleration (e.g., high-speed vehicle accidents, shaken baby syndrome, falls from height).
  • Mechanism involves tearing of white-matter tracts and disruption of brain network connectivity; because injury is widespread and microscopic, CT may be normal while MRI reveals characteristic changes.
• Imaging strategy and findings
  • If NCCT is normal but clinical suspicion remains high, MRI without contrast is the next step, given its superior sensitivity for DAI-related injuries.
  • MRI findings in DAI can include tiny petechial hemorrhages at the gray-white matter junction, visible on GRE or susceptibility-weighted imaging (SWI) sequences.
  • A GRE sequence on MRI can show dark foci at gray-white junctions, indicating microhemorrhages from shearing injuries.
• Prognosis and clinical implications
  • DAI often leads to prolonged coma or severe, lasting disability; prognosis is generally poor compared to focal injuries.
  • Imaging findings can be disproportionate to clinical exam: patients may have profound deficits with relatively subtle imaging.
• Practical notes and implications
  • CT is often negative in early DAI; MRI is more sensitive to microhemorrhages and white matter shearing.
  • The case emphasizes the need for a high index of suspicion for DAI in unconscious patients with normal NCCT and the importance of MRI (especially GRE/SWI sequences) for detection.
• Summary takeaways for Case 4
  • Normal NCCT does not exclude severe diffuse injury; pursue MRI (without contrast) with GRE/SWI sequences to evaluate DAI.
  • DAI carries a poor prognosis; early recognition influences prognosis discussions and management planning.

Case 5: Young patient with sudden severe headache, confusion, and focal weakness suggests vascular malformation

• Presentation and context
  • 28-year-old female with sudden severe headache, confusion, and right-sided weakness.
  • Young age raises suspicion for vascular malformation (e.g., AVM) rather than typical hypertensive hemorrhage seen in older adults.
• Imaging approach and rationale
  • Immediate NCCT to assess for acute hemorrhage is standard in ED evaluation.
  • Given younger age and suspicion for a vascular malformation, CTA (CT angiography) or MRA (MR angiography) is used to evaluate cerebral vessels and detect AVMs or other vascular anomalies.
  • DSA (catheter angiography) is described as the gold standard for detailed vascular mapping to define nidus and feeding arteries/early draining veins.
• AVM imaging features and anatomy
  • AVM nidus: tangled cluster of abnormal vessels; a high-flow connection from arteries to veins.
  • CTA/MRA findings: curvilinear structures and dilated feeding arteries with early draining veins; nidus visualization is key.
  • Catheter angiography (DSA) provides a definitive road map for potential surgical or endovascular treatment planning.
• Pathophysiology and clinical implications
  • AVMs are often congenital and can rupture, causing intracranial hemorrhage; young patients may present with hemorrhagic events due to AVMs.
  • The nidus is fragile due to high-flow shunting; rupture risk is elevated in AVMs.
• Case-specific imaging notes and pitfalls
  • CT may show a hematoma if rupture has occurred; in unruptured AVMs, CT may show a hyperdense serpentine mass and surrounding gliosis with calcifications.
  • CTA/MRA show curvilinear vessel patterns and dilated feeding arteries; small lesions near major dural venous sinuses can be challenging to diagnose; some lesions may require repeat angiography if initial studies are unrevealing.
• Summary takeaways for Case 5
  • In young patients with acute severe headache and focal deficits, vascular malformations (AVMs) should be high on the differential.
  • The diagnostic pathway includes NCCT → CTA/MRA; DSA remains the gold standard for detailed nidus mapping and treatment planning.
  • Be aware of CT features of AVMs: hyperdense serpentine mass, calcifications, gliosis; CTA/MRA findings of nidus and abnormal feeders/early venous drainage.

General imaging principles and clinical reasoning highlights (from the session)

• Imaging modalities and their roles
  • Non-contrast CT (NCCT): first-line in emergency evaluation to rapidly rule out hemorrhage; fast, widely available; identifies hyperdense blood.
  • MRI: more sensitive for acute ischemia via DWI; limitations include time, contraindications, and availability; key sequence is DWI with ADC for diffusion restriction confirmation.
  • DWI and ADC concepts
  • Diffusion-weighted imaging highlights restricted water movement in acute infarct; bright on DWI indicates acute injury.
  • ADC (apparent diffusion coefficient) measures diffusion magnitude; decreased ADC confirms restricted diffusion with acute ischemia.
  • Expression: ext{DWI}_{ ext{acute}}
    ightarrow ext{hyperintense (bright)}, \ ext{ADC} o ext{decreased}
  • CT perfusion (CTP) and CT angiography (CTA) / MR angiography (MRA)
  • CTP helps identify penumbra and tissue at risk; used to stratify patients for interventions when time to treatment is critical.
  • CTA/MRA assess vessel patency and anatomy, including occlusions/stenoses and vascular malformations.
  • Digital subtraction angiography (DSA)
  • Considered the gold standard for detailed vascular anatomy and nidus mapping in AVMs or other vascular lesions; used to guide treatment planning.
• Hemorrhage vs ischemia imaging cues
  • Hemorrhage on NCCT appears hyperdense (bright); hemorrhages may obscure underlying pathology if contrast is used improperly.
  • Ischemia on NCCT can be subtle early; MRI DWI is most sensitive for early ischemia detection.
  • Subarachnoid hemorrhage shows blood within CSF spaces; CT signs can be star/basal patterns; lumbar puncture with xanthochromia may be used if CT is negative and suspicion remains.
• Time course and tissue changes (hemorrhage evolution) — MRI signals by phase (conceptual, per lecture)
  • Hyperacute (first hours): fresh blood; T1 may appear darker; T2 may show variable signal due to oxygenated blood components.
  • Acute: deoxyhemoglobin predominates; signal tends to be dark on T1 and T2 in some sequences.
  • Subacute (days to weeks): methemoglobin formation; T1 and T2 both may appear bright.
  • Chronic (weeks to months): iron deposition (hemosiderin) causing dark signal on multiple sequences.
• Practical clinical strategy in suspected stroke
  • Always consider age and presentation when forming differential diagnoses; young patients with focal neuro deficits may have non-typical etiologies (e.g., AVM, SAH from vascular malformations).
  • The goal is accurate and rapid identification of bleed to guide treatment decisions (ischemic therapy vs hemorrhagic management).
  • Rationale in orders and imaging: phrase in terms of what you are seeking (e.g., identify vessel occlusion, map nidus, assess perfusion, rule out hemorrhage) rather than broad “rule out” language—helps with systems and payer considerations.
• Case-following clinical management and learning points
  • Case 1 emphasizes using NCCT first, then MRI and vessel imaging to confirm acute infarct and plan interventions.
  • Case 2 emphasizes recognition of hypertensive vascular pathology, microbleeds, and evolution of hemorrhage on imaging; importance of microbleeds as part of vascular risk.
  • Case 3 highlights classic traumatic hemorrhage types, their shapes, and localization, plus the role of CT in rapid trauma assessment.
  • Case 4 demonstrates DAI as a scenario where imaging may be unrevealing early with CT but show microhemorrhages on MRI GRE/SWI; prognosis is usually poor.
  • Case 5 demonstrates young patient with potential AVM; emphasis on DSA for definitive mapping and planning; CTA/MRA can image feeders and draining vessels; CT may show hemorrhage or a serpentine mass with calcifications.
• Practical exam and differential-building considerations (case discussion guidance)
  • Build differential diagnoses based on patient age and chief complaint; revise as history and examination reveal more details (onset, progression, aggravating/alleviating factors, past medical history, ROS).
  • In diabetes or systemic disease (demonstrated in later discussion), conduct a head-to-toe examination and comprehensive review of systems; plan labs and imaging accordingly.
  • Diabetes management notes from the session:
  • HbA1c and regular A1c testing every 3 months if not within target progression; target HbA1c commonly around 7% (per discussion).
  • Consider CMP and vitamin B12 levels; B12 deficiency can contribute to neuropathies.
  • Consider vitamin D testing in some contexts.
  • Physical examination emphasis for neuropathy/diabetic patients:
  • Neuro exam: vibratory sense, proprioception, light touch, dermatome mapping, reflexes (hyporeflexia in neuropathy possible), compare bilateral extremities, document stocking-glove distribution of sensory loss.
  • Head-to-toe exam approach and the role of a structured checklist (adult head-to-toe resources referenced).
  • Case-based clinical reasoning tips:
  • Ask and document onset clearly to differentiate acute vs chronic processes.
  • Identify aggravating vs alleviating factors (e.g., gabapentin relief suggests neuropathic pain component).
  • Assess how chronic conditions (e.g., diabetes) influence presentation, prognosis, and management.
  • Be mindful of multiple contributing systems (neuro, MSK, endocrine) and the need for multidisciplinary follow-up (podiatry, endocrinology, etc.).

Ethical, philosophical, and practical implications discussed in the session

• Emphasizes interactive learning and student engagement (raise hand, chat) to reinforce clinical reasoning and imaging interpretation.
• Encourages a broad differential initially and avoidance of tunnel vision; importance of considering alternative etiologies (especially in younger patients) to prevent missing critical diagnoses.
• Highlights the limitations of imaging modalities (availability, contraindications, patient stability) and the need to tailor imaging choices to the clinical scenario.
• Discusses the role of patient-centered care and multidisciplinary planning in chronic diseases (e.g., diabetes) where long-term management, prevention, and follow-up are essential beyond acute imaging findings.

Key numerical references and LaTeX-formatted expressions

• Time-sensitive considerations (conceptual): Time to treatment is crucial in stroke management; immediate imaging decisions influence treatment eligibility.
• Hemorrhage evolution (MRI signal changes by phase):
  • Hyperacute (first hours): T1 ext{ hyperintensity? or darker than normal (as described)}; \, T2 ext{ hypointense (dark)}; blood components reflect deoxyhemoglobin.
  • Acute: ext{Deoxyhemoglobin present; } T1 ext{ and } T2 ext{ are darker (hypointense) in some sequences.}
  • Subacute (days–weeks): ext{Methemoglobin formation; } T1 ext{ and } T2 ext{ become hyperintense (bright).}
  • Chronic (weeks–months): ext{Hemosiderin/iron deposition; signal becomes hypointense (dark) on multiple sequences.}
• Diffusion imaging and diffusion restriction:
  • DWI: acute infarct appears bright due to restricted diffusion;
  • ADC: restricted diffusion corresponds to decreased ADC values: ext{ADC} o ext{decrease in ischemia}.
• Vessel anatomy terms used in AVM case:
  • NidUS: tangled cluster of abnormal vessels;
  • Early draining veins: venous anatomy showing rapid drainage.
• Abbreviations and terms
  • NECT: non-enhanced CT, synonymous with NCCT.
  • DSA: digital subtraction angiography (catheter-based angiography); gold standard for vascular mapping.
  • CTA: CT angiography; MRA: MR angiography.
  • GRE: gradient recalled echo (MRI sequence used to detect microhemorrhages).

Connections to prior lectures and real-world relevance

• This notes set ties directly to imaging modalities and stroke assessment discussed in earlier lectures (CT vs MRI roles, diffusion imaging principles, perfusion imaging, and vascular imaging techniques).
• Real-world relevance: Rapid decision-making in suspected stroke requires applying imaging findings quickly to determine eligibility for reperfusion therapies and to differentiate ischemic vs hemorrhagic etiologies.
• Practical applications include recognizing the imaging signatures of common traumatic and vascular pathologies (EDH, SDH, SAH, DAI, AVM) and understanding how to proceed with multimodal imaging to guide management.

Notes on risk factors and systemic considerations

• Hypertension as a risk factor for intracerebral hemorrhage due to small-vessel fragility: deep intracranial structures (basal ganglia, thalamus) are commonly affected.
• Diabetes mellitus and neuropathy as chronic risk factors: emphasize comprehensive management and monitoring (HbA1c every 3 months if needed; renal and nutritional considerations via CMP and B12; vitamin D as appropriate).
• Multidisciplinary follow-up and careful physical examination are essential in complex cases (head-to-toe exams, ROS, differential diagnosis broadening, and targeted imaging).

End of notes for Cases 1–5