Neuroradiology lecture aug2007

Diagnostic Imaging Methods in Central Nervous System Disorders P Danilo J Lagamayo, MD Headache: Primary: Migraine Cluster Tension Secondary: Increased Intracranial Pressure: Neoplasms Abscess Granulomas Meningeal Irritations: Meningitis Subarachnoid Hemorrhage Vascular Disorders: Stroke Malformations Arteritis Head Trauma: Concussion Hematoma Other Cranio-Facial Pains: Trigeminal Neuralgia Incidence of Primary Brain Tumors: - persons / 100,000 population / year - about in 12 primary brain tumors occur in children under 15 years old Clinical Presentation of Brain Tumors: Focal neurologic deficit Increase intracranial pressure: Headache that is more severe in AM - Nausea / Vomiting - Diplopia - Papilledema - Ontundation & Lethargy (ominous) Focal neurologic signs and symptoms: - seizure, seen in about ½ of Clinical Presentation of Brain Tumors: (II) Non-localizing findings: - fatigue - malaise - impotense - glactorrhea growth failure - macrocephaly in young children Pathological Classification of Intracranial Tumors: Neuroepithelial: Astrocytes Astrocytoma Oligodendrocytes - Oligodendroglioma Ependymal cells & Choroid PlexusEpendymoma Choroid Plexus Papilloma Neurons Gangliomas, Gangliocytomas, Neuroblastomas Pineal cells Pineocytomas Pineoblastomas Poorly differentiated Pathological Classification of Intracranial Tumors: (cont.) Meninges - Meningioma Nerve sheet cells Neuroma - Neurofibroma Blood vessels - Hemangioblastomas Germ cells - Germinoma - Teratoma Tumors of maldevelopmental origin Craniopharyngioma - Epidermoid/Dermoid cyst Pathological Classification of Intracranial Tumors: Anterior pituitary gland - Pituitary adenoma - Adenocarcinoma Local extension - Chordoma from adjacent - Glomus jugulare tumors - Chondroma - Chondrosarcoma - Cylindroma Incidence of Tumors: Glioblastoma - - - - - - - - 55% Astrocytoma - - - - - - - - 20.5% Ependymoma - - - - - - - 6% Medulloblastoma - - - - - 6% Oligodendroglioma _ - - 5% Choroid Plexus Papilloma 2% Other less common entities: Neuronal tumors – Gangliocytomas, ganglioglioma Embryonal – PNET Pineal Region – germ cell Primary Imaging Methods for Diagnosis of CNS tumors: - MRI - CT scan - Angiography In older model CT Scan where volume measurement is not available, an alternative method is possible by using the area of the hemorrhage: Volume in cubic cm = Area x slice thickness (millimeters) 1000 ABC/2 Method: Kothari, et al., has developed a simple bedside method of ICH volume determination with the following formula: ICH volume = A x B x C ABC/2 Method (continued): Step 1: The largest dimension of the hemorrhage is determined in the series of CT slices, then the largest diameter of the hematoma is measured and labeled - A; Step 2: On the same slice, the largest diameter of hemorrhage 90o to A is determined and labeled – B ABC/2 Method (continued): Step 3: “C” or the cephalocaudal dimention of the hemorrhage is determined by comparing the rest of the CT slices to the largest hemorrhage on the scan If the hemorrhage area is 75 % of the largest hemorrhage area = one (1) slice for determining C; ABC/2 Method (continued): Step 3: If the area was 25 to 75% of the slice where the hemorrhage was largest, the slice is considered as one-half a hemorrhage slice; If the area was less than 25 % of the largest hemorrhage, this is not considered as a hemorrhage slice When the CT slice thickness is smaller than the table movement, as will be commonly encountered in CT slices of the posterior fossa, there will necessarily be the presence of inter-slice gaps To remedy this, use the table movement measurement for thickness of the slice instead of the actual slice thickness to calculate for volume (2) A B “1” slice ABC/2 Method: (A x B x C ) ÷ = Volume in cc A = 4.0 cm B = 2.6 cm C = 2.5 cm (4.0 x 2.6 x 2.5) ÷ = 13 cc Actual computation directly done in the CT scan = 13.3 cc Reliability & Reproducibility of the ABC/2 Method of Measuring Intraparenchymal Hemorrhage Volume Reader No Intraclass Correlatio n Difference From Planimetric,* cm3 P† Mean Time per Measurement,‡ s (Neurosurgery faculty) 20 99 -2.0 ± 1.2 11 35 (Neurosurgery resident) 20 99 0.6 ± 3.0 85 40 (Emergency physician) 20 99 0.8 ± 1.3 55 33 (Nurse) 20 Interrater reliability (readers 1-4): Intrarater reliability (reader 3): 99 -2.5 ± 1.5 07 31 Interclass correlation = 99 Interclass correlation = 99 (P=.19) * Mean±SE difference from planimetric measurement † Difference from planimetric measurement ‡ Mean time to determine hemorrhage volume per CT scan with the ABC/2 technique Mean Hemorrhage Volumes Hemorrhage Volume, cm3 Location No Planimetric ABC/2 R2 Deep 83 23.0 ± 2.7 23.5 ± 2.9 94 Lobar 21 44.6 ± 8.4 49.9 ± 9.9 96 Brain Stem 13.6 ± 7.2 12.3 ± 6.3 99 Cerebellar 19.6 ± 4.3 24.4 ± 5.9 78 118 26.0 ± 2.6 27.5 ± 2.9 96 Total Hemorrhage volumes are mean ± SE Temporal Evolution of ICH Biochemical Form Clinical Stage Approximate Time of Appearance OxyHg in RBCs Hyperacute Immediately to first several hours DeoxyHg in RBCs Acute Hours to days MetHg in RBCs Early subacute First several days Extracellular MetHg Subacute to chronic Days to months Ferritin and Hemosiderin Remote Days to indefinitely Temporal Evolution of ICH Biochemical Form Intensity on T1WI Intensity on T2WI ≈  DeoxyHg in RBCs ≈,  MetHg in RBCs   Extracellular metHg   Ferritin and hemosiderin ≈,  OxyHg in RBCs Acute Infarction findings in MRI: Lesion in arterial distribution High intensity in Proton density or in T2 FLAIR Gyral swelling / sulcal effacement Absent arterial flow void Subcortical white matter hypointensity Intravascular contrast enhancement Diffusion weighted imaging: -Signal attenuation is noted in areas of free diffusion Signal intensity is increased in areas of restricted diffusion with decrease in apparent diffusion coefficient in brain tissue - Decrease in diffusion of water in early ischemia is due to shift of water from extracellular to intracellular