Neuroradiology for Medical Students

1. Neuroradiology for Medical Students

2. By the end of this tutorial, you will be able to recognize some of the common radiologic problems most often seen by physicians. Hopefully, you will also become more aware of what tests to order and when to order them. We also hope that you will have a little fun in the process!

3. CT Anatomy (you kind of need to know this) A = Frontal sinus B = Orbit C = Frontal lobe D = Sphenoid sinus E = Temporal lobe F = External auditory canal G = Mastoid air cells H = Cerebellar tonsil I = Foramen magnum

5. A = Falx B = Frontal horn of the lateral ventricle C = Caudate nucleus D = Internal capsule (anterior limb) E = Sylvian fissure F = Basal ganglia G = Third ventricle H = Quadrigeminal plate cistern I = Cerebellum

6. A = Interhemispheric fissure B = Genu of the corpus callosum C = Frontal horn of the lateral ventricle D = Internal capsule E = Thalamus F = Pineal gland (calcified) G = Cerebellar vermis H = Straight sinus

7. A = Falx cerebri B = Frontal lobe C = Parietal lobe D = Body of the lateral ventricle E = Occipital lobe

8. A = Falx cerebri B = Sulcus C = Gyrus D = Central sulcus E = Superior sagittal sinus

9. MRI Anatomy (this is kind of really important too) A = Internal carotid artery B = Medulla C = Cerebellar hemisphere D = Maxillary sinus E = Sigmoid sinus F = External auditory canal

10. A = Sphenoid sinus B = Internal carotid artery C = Temporal lobe D = Fourth ventricle E = Basilar artery F = Pons G = Middle cerebellar peduncle H = Cerebellum

11. A = Orbit B = Optic chiasm C = Hippocampal formation D = Cerebral peduncle E = Tegmentum (midbrain) F = Cerebral aqueduct G = Tectum (midbrain) H = Quadrigeminal cistern I = Occipital lobe

12. A = Caudate nucleus B = Anterior limb of the internal capsule C = Putamen D = Fornix E = Posterior limb of the internal capsule F = Insula G = Thalamus H = Lateral ventricle (posterior horn) I = Corpus callosum (splenium)

13. A = Lateral ventricle B = Caudate nucleus C = Septum pellucidum D = Sylvian fissure E = Corpus callosum (genu) F = Gray matter G = White matter

14. Coronal MRI Anatomy A = Intrahemispheric fissure B = Corpus callosum C = Lateral ventricle D = Suprasellar cistern E = Temporal lobe F = Insular cortex G = Sylvian fissure

15. A = Superior sagittal sinus B = Corpus callosum C = Septum pellucidum D = Lateral ventricle E = Caudate nucleus F = Internal capsule G = Interventricular foramen of Monro H = Third ventricle I = Insular cortex

16. A = Corpus callosum (splenium) B = Choroid plexus of the lateral ventricle C = Hippocampal formation D = Quadrigeminal cistern E = Fourth ventricle F = Cerebellar hemisphere G = Tentorium cerebelli

17. Sagittal MRI Anatomy A = Corpus callosum B = Fornix C = Thalamus D = Optic chiasm E = Pituitary gland F = Pons G = Dens (C2 vertebra) H = Spinal cord I = Pineal gland J = Tectum (midbrain) K = Cerebral aqueduct L = Tegmentum (midbrain) M = Fourth ventricle N = Medulla

18. Circle of Willis A = Basilar artery B = Posterior cerebral artery C = Thalamoperforators D = Posterior communicating artery E = Internal carotid artery F = Middle cerebral artery G = Anterior cerebral artery H = Anterior communicating artery

19. Vascular Territories A = Anterior cerebral artery B = Middle cerebral artery C = Posterior cerebral artery D = Lenticulostriate arteries

20. A 82 y/o female presents with sudden onset of right-sided weakness and garbled speech for 3 hours. What, if any, radiologic test would you order, and why? Read about the following imaging techniques to help you formulate an answer:

21. Imaging Techniques

22. CT vs. MRI: What to order? CT • Acuteneurological events: • Stroke • Trauma • Worst HA of life • Acute mental status change • First seizure • Neurosurgery immediate post-op • Follow up: • Acute infarcts • Hemorrhage • Hydrocephalus MRI • Acute (usually after CT): • Stroke • Encephalitis • Subacute and chronic: • Progressive, subacute, or chronic neurological deficit • TIAs, h/o of stroke • Brain tumors • Metastatic disease • Dementia • Epilepsy • Chronic headaches • MS • Developmental delay • Pituitary disorders • Cranial nerve dysfunction

23. CT Head • For acute neurologic eventsCT of the head without IV contrast • The most frequent reason that a CT head is ordered is for the diagnosis of CVA’s and ICH • Does not exclude infarct in acute stage of a stroke, but is useful to exclude a bleed (so anticoagulant medication can be commenced) • IV contrast is not routinely used, but may be useful for evaluating tumors, cerebral infections, and sometimes for the evaluation of stroke patients.

24. CT Head • CT can also be used to detect increases in intracranial pressure, e.g. before lumbar puncture or to evaluate the functioning of a VP shunt. • CT is used in trauma for evaluating facial and skull fractures. • In order to prevent unnecessary irradiation of the orbits and especially the lenses, head CTs are performed at an angle parallel to the base of the skull, with the patient in the supine position. • Slice thickness generally is between 5 and 10 mm

25. MRI • MRI is also performed for possible brain stem and posterior brain pathology, that is not readily seen on CT • Currently, MRI with Diffusion Weighted Imaging: • Is superior to CT in detecting acute infarcts • Is less sensitive than CT for SAH and hyperacute parenchymal hemorrhage • Has no exposure to radiation, but takes longer to get study done

26. Imaging Techniques

27. Imaging Techniques Normals CT vs. MRI-T1 vs. MRI-T2

28. Imaging Techniques

29. CT Angiography (CTA) • Advantages: • Noninvasive • Faster than MRA or Angiography • Excellent for measuring lesions • Easily demonstrates intraluminal clots and extravascular hematomas • Disadvantages: • Radiation exposure • Use of contrast material • Can be diagnostic, but may require invasive therapeutic measures

30. Magnetic Resonance Angiography (MRA) • Advantages: • -Noninvasive • -Iodinated Contrast not needed • -Safe for patients with renal insufficiency • -Images can be reconstructed in any plain • -Does not require the use of radiation • -Depicts both anatomy and flow rate • Disadvantages: • -Can not be used in patients with pacemakers or certain hardware • -Long acquisition time • -Poor spatial relations • -Can be diagnostic but may require invasive therapeutic measures

31. Angiogram • Advantages: • Can be diagnostic and theurapeutic • Although invasive, if a clot or aneurysm is seen, intervention can be done at the time of the procedure • Disadvantages: • Invasive • Use of Contrast Material • Possible Kidney failure • Lengthy post-procedure precautions for bleeding from insertion site

32. A 82 y/o female presents with sudden onset of right-sided weakness and garbled speech for 3 hours. What, if any, radiologic test would you order, and why? Answer: CT of head without IV contrast. Why, you ask? As you can see from the above info, both IV contrast and an acute bleed will show up bright on CT. You must first rule out hemorrhage in any acute stroke patient, so that appropriate therapy can be started. You wouldn’t want to start thrombolytic therapy on someone who is actively bleeding!!!

33. Mini Quiz Which of the following is NOT true concerning the process of performing a head CT? A. Head CTs are performed at an angle parallel to the base of the skull. B. Slice thickness is generally between 5 and 10 mm. C. Intravenous contrast is routinely used. D. The patient is placed in a supine position on the table.

34. Stroke

35. 68 y/o with left-sided weakness and confusion CT Head w/o Contrast

36. Ischemic Stroke • Ischemic strokes account for 84% of all strokes • Causes: • Thrombosis • Blood clot forms in one of the cerebral arteries from hypercoagulable state, rupture of atherosclerotic plaque, or underlying stenosis • May be preceded by transient ischemic attack (TIA) • Embolism • Detached clot from heart or large vessels such as carotid • Afib is a common cause • Hypoperfusion • Proximal stenosis of cerebral artery • Cardiac or respiratory failure • Lacunar infarctions • walls of small arteries thicken and cause the occlusion of the artery • involve the small perforating vessels of the brain and result in lesions that are less than 1.5 cm in size. Sharply circumscribed hypodense edema (arrowheads) in the right middle cerebral artery territory

37. Early CT findings in acute infarct • May be normal in first ~ 12 hours • Loss of gray-white matter differentiation • Loss of bright cortical ribbon • Subtle hypodensity (cytotoxic edema) • Loss of bright basal ganglia • Swelling/sulcal effacement • Hyperdense artery sign • Artery must be brighter than other Circle of Willis arteries • Artery in question must fit clinical picture CT showing acute infarct with loss of gray-white matter differentiation (arrows) and sulcal effacement

38. 79 y/o female with HA and ataxia CT Head w/o contrast

39. Hemorrhagic Stroke • Hemorrhagic strokes are due to rupture of a cerebral blood vessel that causes bleeding into or around the brain. • 2 Types (intracerebral and subarachnoid) • Intracerebral • Hypertensive hemorrhage (most common cause) • Predilection for deep structures of the brain, such as thalamus, pons, cerebellum, and basal ganglia • Amyloid angiopathy • Ruptured vascular malformation • Coagulopathy • Hemorrhage into a tumor • Drug Abuse Hemorrhage in the left posterior parietal lobe (arrow)

40. 28 y/o female with “worst HA of my life” CT head w/o contrast

41. Subarachnoid Hemorrhage • Main causes: • Trauma #1 • Ruptured cerebral aneurysm • Other Causes: • AVM rupture • Coagulopathy • Vasculitis • Neoplasm • Pituitary apoplexy • Hypertension • Venous rupture/venous thrombosis • NONCONTRAST CT is the imaging of choice for nontraumatic SAH • If CT is negative and there is still a strong clinical suspicion→ LP may be used for the diagnosis • Detection of a subarachnoid hemorrhage is crucial because the rehemorrhage rate of ruptured aneurysms is high and rehemorrhage is often fatal. • On CT, a subarachnoid hemorrhage appears as high density within sulci and cisterns. High density blood fills the third ventricle and is in the sylvian fissure in this subarachnoid hemorrhage.

42. After positive SAH on CT or lumbar puncture: • Cerebral (catheter) angiography: “Gold standard” • Invasive • Time and labor intensive • Small risk of complications (stroke, contrast reaction) • CTA—best first exam; replaces cerebral angiography in many cases • Minimally invasive (IV injection) • Very fast • Moderately labor intensive • May still need catheter angiography if CTA is negative, or aneurysm not well delineated • Iodinated contrast risk

43. 25 y/o with new onset seizures CT head w/o contrast

44. Arteriovenous Malformation with Hemorrhage • Underlying AVM may or may not be visible on CT scan • Prominent vessels adjacent to the hematoma suggest an underlying arteriovenous malformation • Some arteriovenous malformations contain dysplastic areas of calcification and may be visible as serpentine enhancing structures after contrast administration. The CT on the top shows hemorrhage (arrow) due to underlying AVM (arrowheads). The arteriogram on the left shows the tangle of vessels (arrowheads) of the AVM. This lesion would be considered for intravascular embolic therapy.

45. The most important issue to determine when imaging a stroke patient is whether a hemorrhagic or ischemic event has occurred. B. False A. True

46. A. Hemorrhagic stroke is more common than ischemic stroke. Which of the following is NOT true concerning stroke? B. An embolic stroke occurs when a detached clot flows into and blocks a cerebral artery.C. Global anoxia presents an ischemic challenge to the brain and is classified as a hypoperfusion infarction.D. The most common cause of non-traumatic intracerebral hematoma is hypertensive hemorrhage.

47. In which of the following locations is hypertensive hemorrhage LEAST LIKELY to occur? A. Thalamus B. Cerebellum C. Basal Ganglia D. Pons E. Occipital Lobe

48. Which of the following is NOT true concerning CT of a stroke patient? A. Patients who have a hypertensive hemorrhage may have extension of blood into the ventricular system. B. An acute infarct may be normal on CT for the first 12 hours. D. On CT, prominent vessels adjacent to a hematoma suggest an underlying arteriovenous malformation. C. The underlying arteriovenous malformation causing stroke is almost always visible on CT scan.

49. Which of the following is NOT a CT finding in an acute infarct? A. Loss of gray-white distinction B. Subtle hypodensity due to cytotoxic edema C. Hyperdensedense basilar or middle cerebral artery corresponding to thrombus in the affected vessel. E. Sulcal effacement D. Dysplastic areas of calcification

50. Which of the following is NOT true concerning subarachnoid hemorrhage? A. Appears as high density within sulci and cisterns. B. Noncontrast CT is the imaging of choice for suspected SAH. D. Cerebral angiography is the “gold standard.” E. Subarachnoid hemorrhage occurs most commonly with trauma C. The rehemorrhage rate of a SAH is low.