Emergency Imaging. Alexander B. Baxter

Emergency Imaging

Facial bone fracture

Headache

Noncontrast head CT is indicated. Postcon-trast head CT or MRI may be considered in immunocompromised patients, in those with underlying malignancy and concern for metastatic disease, and in patients oth-erwise at risk for brain abscess.

• Subarachnoid hemorrhage

• Venous sinus thrombosis

• Meningitis

• Hydrocephalus

• Cerebral hemorrhage

• Mass (tumor or abscess)

• Sinusitis

• Otitis/mastoiditis

◆Imaging and AnatomyImaging

Head CT (Noncontrast)

Indications: Head injury, altered mental status, seizure, suspected hemorrhage or infarct.

Technique: 5-mm axial images in soft tissue and bone algorithm

Head CT (Noncontrast Helical)

Indications: Head injury with concurrent imaging of the face and cervical spine.

Technique: Helical 0.6-mm dataset with 5-mm axial, 2-mm sagittal, and 2-mm coronal reformations of head, face, and cervical spine. Images obtained from skull vertex to thoracic inlet.

CT Arteriogram

Indications: Subarachnoid hemorrhage.

Suspected aneurysm or vascular malformation. Acute cerebral infarct. Penetrating injury.

Technique: Helical 0.6-mm dataset with 2.5-mm axial, 2-mm sagittal, and 2-mm coronal reformations. Images can be obtained from the vertex either to the skull base or to the thoracic inlet depending on the indication.

Contrast: 60–100 mL at 3–4 mL/sec in arterial phase.

CT Venogram

Indications: Suspected venous sinus thrombosis (atypical headache). Trauma to skull base with potential venous sinus disruption.

Technique: Helical 0.6-mm dataset with

2.5-mm axial, 2-mm sagittal, and 2-mm coronal reformations. Images obtained from vertex to skull base.

Contrast: 60–100 mL at 3–4 mL/sec in venous phase (30–45 sec delay).

12Emergency Imaging

2 Brain

Fig. 2.2a–i Cerebral vascular territories and anat-omy. ACA: Anterior cerebral artery. PCA: Posterior cerebral artery. MCA: Middle cerebral artery. Ach: Anterior choroidal artery. CCA: Common carotid artery. ICA: Internal carotid artery. ECA: External carotid artery. SThA: Superior thyroidal artery. LA: Lingual artery. FA: Facial artery. PA: Posterior auric-ular artery. OC: Occipital artery. IMA: Internal max-illary artery. STA: Super cial temporal artery. BA: Basilar artery. SCA: Superior cerebellar artery. PICA: Posterior inferior cerebellar artery. AICA: Anterior inferior cerebellarartery. PCom: Posterior commu-nicating artery.

14Emergency Imaging

Extraparenchymal Mass

• Meningioma

• Calvarial or dural metastasis

• Epidermoid

•Schwannoma (cranial nerves 5, 8, and 9)

• Arachnoid cyst

• Aneurysm

Sellar and Suprasellar Mass (Mnemonic: SATCHMO)

• Sellar tumor (pituitary adenoma), sarcoidosis

• Aneurysm

• Teratoma (and germ cell tumors)

• Craniopharyngioma

• Hypothalamic glioma

• Meningioma (planum sphenoidale) and metastasis

• Optic glioma

Ring Enhancing Mass (Mnemonic: MAGIC DR)

• Metastasis

• Abscess

• Glioma

• Infarct (evolving)

• Contusion (evolving)

• Demyelinating disease

• Radiation necrosis

Hemorrhagic Metastases (Mnemonic: CT/MR)

• Choriocarcinoma

• Thyroid carcinoma

• Melanoma

• Renal cell carcinoma

Remember that lung and breast carcinoma, even though less frequently hemorrhagic, are much more common and are more likely to be the cause of a hemorrhagic metastasis.

Acute Focal Neurologic Decit

Noncontrast head CT is indicated to exclude hemorrhage in suspected stroke. Noncon-trast head CT should be obtained to detect or exclude cerebral hemorrhage. MRI with a diusion-weighted sequence can conﬁrm the clinical suspicion of infarct in patients whose initial CT appears to be normal. CT or MR angiography and perfusion studies can be obtained to better characterize the extent of ischemia and identify vascular stenoses or occlusion.

• Ischemic infarct

• Lacunar infarct

• Embolic infarct

• Border-zone (watershed) infarct

• Hypertensive hemorrhage

• Amyloid angiopathy with hemorrhage• Ruptured arteriovenous malformation

Altered Mental Status

Noncontrast head CT is indicated. Post-contrast head CT or MRI may be consid-ered in immunocompromised patients, in thosewith underlying malignancy and concern for metastatic disease, in patients otherwise at risk for brain abscess, and to evaluate further subtle abnormalities on noncontrast CT.

• Cerebritis (herpes encephalitis)

• Infarct

• Hemorrhage

• Parenchymal volume loss

• Chronic subdural hematoma

Dierential Diagnoses

Intraparenchymal Mass

• Glioma

• Metastasis

• Lymphoma

• Abscess

• Arteriovenous malformation

2Brain

• Dehydration

• Steroid use

• Chemotherapy

• Remote head injury

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