Study guide
22.4 Arterial Dissection and Carotid-Cavernous Fistula (03.I.5–6)
ABIM Neurocritical Care Subspecialty Certification Exam
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 Eligibility, Practice Pathway, and the IM Training Route 1.3 Format, Scoring, Pearson VUE, and Score Reports 1.4 How to Use This Independent Study Guide
2 ICU Neurologic Exam, Cerebral Physiology, and CSF
2.1 Neurological Examination in the ICU 2.2 Cerebral Physiology, ICP, CBF, and Autoregulation 2.3 CSF Physiology
3 Core Neuropharmacology
3.1 Osmotic Agents 3.2 Anti-Seizure Drugs 3.3 Anesthetics, Sedatives, Analgesia, and Paralytics 3.4 Antihypertensives, Vasopressors, and Inotropes
4 Reperfusion Drugs, Airway, and Ventilation
4.1 Thrombolytics, Anticoagulants, and Antiplatelets 4.2 Reversal of Anticoagulation After Acute Hemorrhage 4.3 Airway Management and Tracheostomy 4.4 Mechanical Ventilation
5 Hemodynamics and Shock
5.1 Hemodynamic Monitoring 5.2 IABP, Temporary VADs, LVAD, and ECMO 5.3 Diagnosis and Management of Shock
6 Nutrition, Temperature, and ICU Prophylaxis
6.1 Nutrition (01.J) 6.2 Temperature Control (01.K) 6.3 ICU Prophylaxis, Delirium, and Early Mobility (01.L)
7 General Trauma
7.1 Emergency Evaluation of Polytrauma, Chest, and Abdominal Trauma 7.2 Long-Bone Fractures and Fat Embolism 7.3 Burns, Electrical Injury, and Hanging/Strangulation
8 Pulmonary Critical Care
8.1 Pulmonary Physiology and ARDS (01.N.1–2) 8.2 PE, Pneumonia, and Pulmonary Edema (01.N.3, 7–8) 8.3 COPD, Asthma, PAH, and Bronchoscopy Basics (01.N.4–6, 9)
9 Cardiovascular Critical Care
9.1 Cardiovascular Physiology, Stress Cardiomyopathy, ACS, and Valves 9.2 Arrhythmias and Pacing 9.3 Acute Aortic Dissection and Cardiac Ultrasound
10 Renal and Infectious Disease
10.1 AKI, RRT, and Renal Drug Dosing 10.2 Acid-Base and Electrolyte Disorders 10.3 Severe Sepsis, Septic Shock, and Infective Endocarditis 10.4 Antimicrobial Use and Infection in the Immunosuppressed
11 Endocrine and Salt-Water Disorders
11.1 Pituitary Apoplexy, DI, and Panhypopituitarism (01.R.1–4) 11.2 SIADH and Cerebral Salt Wasting (01.R.5–6) 11.3 Thyrotoxicosis, Myxedema, Adrenal Crisis, and Dysglycemia (01.R.7–9)
12 Gastrointestinal Critical Care
12.1 GI Physiology, Acute Abdomen, Bleed, Ileus, and Perforation (01.S.1–5) 12.2 Mesenteric Ischemia and Abdominal Compartment Syndrome (01.S.6–7) 12.3 Fulminant Liver Failure, Cirrhosis Decompensation, and Hepatic Dosing (01.S.8–10)
13 Hematologic Disorders
13.1 Anemia, Transfusion, Thrombocytopenia, Coagulopathy, and DIC (01.T.1–4) 13.2 VTE in the Neuro ICU (01.T.5) 13.3 Chemo/Immune, SCT, CAR-T, Sickle Cell, and TMA (01.T.6–10)
14 Neuroimaging
14.1 CT of Brain and Spine 14.2 MRI and CT/MR Perfusion 14.3 Noninvasive Angiography and Catheter Angiography
15 EEG, EMG, and CSF Analysis
15.1 EEG, Standard and Processed (02.B) 15.2 Basic EMG Interpretation (02.G) 15.3 CSF Analysis (02.H)
16 ICP, TCD, and Multimodality Monitoring
16.1 ICP Monitoring (02.C) 16.2 Transcranial Doppler (02.D) 16.3 Brain-Tissue Oxygen and Multimodality Monitoring (02.E–F)
17 Brain Death and Bedside Procedures
17.1 Brain Death Prerequisites and Clinical Exam (02.I) 17.2 Apnea Testing and Ancillary Studies (02.I) 17.3 Vascular Access, Thoracic Echo, and Lung Ultrasound (02.J–L)
18 Coma, Anoxia, and Intracranial Hypertension
18.1 Coma and Other States of Altered Consciousness (03.A) 18.2 Global Anoxia-Ischemia and Post-Resuscitation Encephalopathy (03.A.1) 18.3 Toxidromes, ICU Delirium, and Hypertensive Encephalopathy (03.A.2–4) 18.4 Intracranial Hypertension as a Disease State (03.B)
19 Acute Ischemic Stroke
19.1 IV Reperfusion Therapy (03.C.3) 19.2 Mechanical Thrombectomy Windows and Imaging Selection (03.C.3) 19.3 Malignant Hemispheric Infarction and Basilar Artery Occlusion (03.C.1–2)
20 Intraparenchymal Hemorrhage
20.1 Intracerebral Hematoma (03.D.1) 20.2 Cerebellar Hematoma (03.D.2) 20.3 Intraventricular Hemorrhage (03.D.3)
21 SAH, CVST, and Spinal Cord Infarction
21.1 Aneurysmal Subarachnoid Hemorrhage (03.E.1) 21.2 Non-Aneurysmal SAH (03.E.2) 21.3 Cerebral Venous Sinus Thrombosis (03.F) 21.4 Spinal Cord Infarction (03.G)
22 Vascular Anomalies and Traumatic Brain Injury
22.1 Unruptured Aneurysm, Cavernoma, AVM, and Dural AVF (03.H) 22.2 Diffuse Axonal Injury and Cerebral Contusions (03.I.1–2) 22.3 Epidural Hematoma, Subdural Hematoma, and Penetrating Injury (03.I.3–4, 7) 22.4 Arterial Dissection and Carotid-Cavernous Fistula (03.I.5–6)
23 Spine, Hydrocephalus, and CNS Infection
23.1 Spinal Cord Injury, Central Cord, and Neurogenic Shock (03.J) 23.2 Unstable Spine Fractures (03.K) 23.3 Hydrocephalus and CSF Diversion (03.L) 23.4 Acute CNS Infections (03.M)
24 Seizures and Neuromuscular Emergencies
24.1 Status Epilepticus and Seizures (03.N) 24.2 Guillain-Barré Syndrome (03.O.1) 24.3 Myasthenic Crisis (03.O.2) 24.4 Motor Neuron Disease, Acute Myopathies, Rhabdomyolysis, and CINM (03.O.3–6)
25 Inflammatory Disease, Neuro-Oncology, and Special Populations
25.1 Fulminant Demyelinating Diseases (03.P) 25.2 Autoimmune Encephalitis and Acute Autonomic Hyperactivity (03.Q–R) 25.3 Neuro-Oncology and Treatment Complications (03.S) 25.4 Pregnancy/Post-Partum, Post-Transplant, and Pediatric Patients (03.T–U)
26 Neurosurgical and Perioperative Complications
26.1 Postoperative Seizures, Hemorrhage, Ischemia, and Hyperperfusion (04.A, C, D, H) 26.2 Infection, CSF Leak, and Pneumocephalus (04.B, E, F) 26.3 Complications of EVD and Lumbar Drain (04.G, I)
27 Ethics, Prognostication, and Organ Donation
27.1 Communication, Decision-Makers, Advance Directives, and DNR (05.A, B, G) 27.2 Uncertainties of Prognostication and the Self-Fulfilling Prophecy (05.C) 27.3 Palliative Care, Withdrawal, Withholding, and Futility (05.D–F) 27.4 Donation After Cardiac Death and Care of the Organ Donor (05.H–I)
22.4 Arterial Dissection and Carotid-Cavernous Fistula (03.I.5–6)
Key Takeaways Explain This Topic AI
Cervical internal-carotid and vertebral dissections follow trauma or sudden neck motion (including chiropractic manipulation). Painful partial Horner syndrome (ptosis and miosis) points to the extracranial internal carotid artery.
CADISS found no significant difference between antiplatelet therapy and anticoagulation for uncomplicated extracranial dissection. Concurrent traumatic hemorrhage creates an ischemic-versus-hemorrhagic conflict that delays or forbids full anticoagulation.
Intracranial dissection and blister aneurysms present with subarachnoid hemorrhage far more often than cervical flaps do; they need reconstructive or deconstructive vascular repair, not a CADISS antithrombotic pathway.
Direct (Barrow A) carotid-cavernous fistula is high-flow and usually traumatic: proptosis, orbital bruit, chemosis, and threatened vision. Indirect fistulas are lower flow. DSA defines the shunt; coil or liquid embolization closes it.
Red flags that should move a trauma patient to vascular imaging tonight include a painful Horner, posterior-circulation ischemia after neck manipulation, an orbital bruit with chemosis, and a penetrating tract across the cavernous sinus.
Last updated: September 2026
Blueprint items 03.I.5–6 pair two vascular complications of trauma that the noncontrast head CT can miss. Cervical arterial dissection presents as pain plus ischemia (or a painful Horner). Carotid-cavernous fistula (CCF) presents as a red, noisy, proptotic eye. Both need vascular imaging. Both punish the reflex to start a heparin drip or to pull a foreign body before you know where the internal carotid artery is.
Independent ExamFinch teaching for this ABIM Neurocritical Care topic uses CADISS, Barrow’s CCF types, and standard trauma-angiography practice. It is not an AHA cervical-artery-dissection guideline reprint.
Cervical internal-carotid and vertebral dissection
The cervical internal carotid artery (ICA) and vertebral artery tear when the intima splits and blood enters a false lumen. Triggers that appear on exams are blunt cervical trauma, sudden rotation or extension, coughing or vomiting, and neck manipulation including chiropractic adjustment (especially vertebral). Connective-tissue disease (vascular Ehlers–Danlos, Marfan, fibromuscular dysplasia) lowers the threshold. The mural hematoma can narrow the true lumen, throw artery-to-artery emboli, or expand into a pseudoaneurysm .
ICA dissection announces itself with ipsilateral head, face, or neck pain and a partial Horner syndrome : ptosis and miosis from interrupted oculosympathetic fibers on the ICA. Anhidrosis is often absent because sudomotor fibers travel with the external carotid artery. Hours to days later comes a retinal or hemispheric ischemic event in a young or middle-aged adult. Vertebral dissection produces occipital or cervical pain and posterior-circulation ischemia (lateral medulla, cerebellum, PCA territory) and can extend intracranially and bleed.
Imaging: CTA is the usual first test in trauma. Fat-saturated T1 MRI shows the crescent of intramural methemoglobin. Catheter angiography is reserved for uncertain anatomy, endovascular therapy, or a planned stent. Do not wait for a perfect intramural-hematoma MRI if the CTA already shows a flame-shaped occlusion or a long irregular stenosis after neck trauma.
Antithrombotic therapy versus hemorrhage
Uncomplicated extracranial dissection is treated to prevent artery-to-artery embolism. The CADISS trial (Lancet Neurology 2015; 2019 follow-up) randomized extracranial carotid or vertebral dissection to antiplatelet therapy versus anticoagulation and found no significant difference in ipsilateral stroke or death. TREAT-CAD compared aspirin with a vitamin K antagonist and did not establish aspirin as clearly non-inferior on its original composite; practice still often starts with a single antiplatelet agent when the stroke burden is small and bleeding risk is not zero.
The neuro ICU conflict is not CADISS versus TREAT-CAD. It is ischemic prevention versus traumatic hemorrhage . A patient with a cervical ICA flap plus an acute subdural hematoma, contusions, or traumatic SAH cannot safely receive a heparin infusion on the night of injury. Options: hold antithrombotics until a stability CT, use a single antiplatelet later if the extra-axial blood is small and not expanding, or stent a flow-limiting lesion if the hemisphere is dying and open surgery is not feasible. Recurrent ischemia despite medical therapy, an expanding extracranial pseudoaneurysm, or hemodynamic failure of the true lumen are the usual reasons to stent.
Intracranial dissection and blister aneurysms
Once the tear is intracranial , the wall is thinner and the presentation shifts from embolic stroke toward subarachnoid hemorrhage . Intracranial vertebral dissection is a classic cause of posterior-fossa SAH without a saccular berry aneurysm. Blister aneurysms of the supraclinoid ICA are tiny, fragile, and notorious for intraoperative rupture and early rebleeding. They are treated with reconstructive techniques (overlapping stents, flow diversion, wrapping plus bypass in selected cases) or, if the hemisphere has collateral flow, deconstructive sacrifice. They are not CADISS lesions. Anticoagulation after a blister or intracranial-dissection SAH is contraindicated until the segment is secured.
Carotid-cavernous fistula: direct versus indirect
The cavernous sinus is a venous plexus that contains the ICA and cranial nerves III, IV, V1, V2, and VI. A CCF is an abnormal shunt into that plexus.
Barrow classification:
Type Anatomy Flow Typical story
A (direct) Tear in the cavernous ICA itself into the sinus High Trauma, skull-base fracture, iatrogenic; sudden red eye
- B Meningeal branches of the ICA Low Spontaneous, often older women
- C Meningeal branches of the ECA Low Spontaneous
- D ICA and ECA meningeal feeders Low Spontaneous
Direct (high-flow, traumatic) CCF is the ICU lesion. The patient develops proptosis, chemosis, a pulsatile orbital bruit , diplopia, and rising intraocular pressure. Vision is the organ you can still lose after the fracture is plated. Cortical or posterior-fossa venous drainage turns a “eye problem” into an intracranial-hemorrhage problem. Indirect (dural, low-flow) fistulas present more quietly and sometimes thrombose; they still need treatment if vision is threatened or CVD is present.
Digital subtraction angiography (DSA) remains the definitive map of the rent, the steal, and the venous outlets (superior ophthalmic vein, inferior petrosal sinus, cortical veins). CTA or MRA can suggest the diagnosis when the superior ophthalmic vein is arterialized and enlarged. Treatment is endovascular closure : transarterial coils or liquid embolic across a direct rent with ICA preservation if possible; transvenous packing of the cavernous sinus for many indirect fistulas. Urgent cases are falling vision, uncontrolled intraocular pressure, and CVD. Do not temporize a direct high-flow traumatic CCF with lubricating drops and a planned “outpatient ophthalmology follow-up.”
Red flags that should force vascular imaging tonight
Red flag Likely lesion First move
Painful partial Horner after trauma or neck strain Cervical ICA dissection CTA of neck and head; hold full anticoagulation if intracranial blood is present
Occipital pain and crossed brainstem signs after chiropractic manipulation Vertebral dissection CTA; treat ischemia; look for intracranial extension / SAH
Thunderclap plus posterior-fossa SAH and no berry aneurysm Intracranial VA dissection or blister DSA and repair, not CADISS anticoagulation
Proptosis, chemosis, orbital bruit after skull-base fracture Direct (Barrow A) CCF Urgent DSA; coil or embolize; protect vision
Impaled object or tract through the cavernous sinus Traumatic CCF, ICA injury, or both Leave the object; CTA/DSA; OR with endovascular backup
Delayed monocular visual loss and a red eye days after facial fractures Missed CCF Do not call it conjunctivitis; listen for a bruit and image
Recurrent hemisphere TIA despite antiplatelet after known cervical dissection Flow-limiting flap or pseudoaneurysm Repeat CTA; consider stent
Expanding cervical hematoma and a noisy neck after penetrating trauma Extravasation or fistula Airway first, then angiography
Worked conflicts
A 41-year-old has a rollover crash, a small traumatic SAH, and a painful Horner. CTA shows a cervical ICA dissection with 70% narrowing. Starting a heparin drip tonight treats the CADISS-style lesion and expands the SAH. The correct sequence is stability imaging, blood-pressure control that avoids both hypoperfusion and aneurysm-range spikes, and a delayed antiplatelet once the extra-axial blood is quiet — or a stent if the hemisphere infarcts on the table.
A 28-year-old with a basilar skull fracture develops a pulsatile red eye and a bruit the nurses can hear without a stethoscope. Visual acuity is falling. That is a direct high-flow CCF until DSA says otherwise. Coils or a covered reconstruction close the shunt; lubricating ointment does not.
A 55-year-old develops thunderclap headache after a trivial neck strain. CT shows prepontine SAH. CTA is “negative for berry aneurysm.” The next study is catheter angiography aimed at intracranial vertebral dissection or a blister , not a prescription for warfarin because “CADISS allows anticoagulation.”