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Transient cerebral ischemia is defined as a temporary loss of blood flow to an area in the brain. In ICD-9-CM, codes for transient cerebral ischemia are classified under circulatory system diseases and are found in Chapter 7, Diseases of the Circulatory System. Conditions classified as transient cerebral ischemia are listed in category 435 and include basilar artery syndrome (435.0), vertebral artery syndrome (435.1), subclavian steal syndrome (435.2), and vertebro-basilar artery syndrome (435.3).

There are also codes for other specified types of transient cerebral ischemia (435.8) and unspecified type (435.9). The code for unspecified transient cerebral ischemia is used for a diagnosis of transient ischemic attack (TIA).

In ICD-10-CM, transient cerebral ischemic attacks and related syndromes are classified as nervous system diseases and are found in Chapter 7, Diseases of the Nervous System. Category G45 includes codes for vertebro-basilar artery syndrome (G45.0), carotid artery syndrome (G45.1), multiple and bilateral precerebral artery syndromes (G45.2), other transient ischemic attacks and related syndromes (G45.8), and unspecified transient cerebral ischemic attacks (G45.9). Also included in category G45 are codes for amaurosis fugax (G45.3) and transient global amnesia (G45.4). Amaurosis fugax is a type of transient cerebral ischemia, but the condition affects only the eyes; in ICD-9-CM, this condition is classified in Chapter 6, Nervous System and Sense Organs, with conditions affecting the eyes (362.34). In ICD-9-CM, transient global amnesia (437.7) is classified as a disease of the circulatory system and listed in the category for other and ill-defined cerebrovascular disease.

Vertebro-Basilar Artery Syndrome Codes

In ICD-9-CM, three codes are provided in category 435 for transient ischemic syndromes related to basilar and/or vertebral artery circulation. Again, these include 435.0 (basilar artery syndrome), 435.1 (vertebral artery syndrome), and 435.3 (vertebro-basilar artery syndrome). In ICD-10-CM, a single code, G45.0 Vertebro-basilar artery syndrome, covers the same conditions indicated by the three codes in ICD-9-CM. In order to understand why these conditions have been reclassified and combined into a single code in ICD-10-CM, it is necessary to review the medical terminology, anatomy, and pathophysiology related to these conditions.


The term “syndrome” refers to multiple symptoms and signs that together represent a specific condition, disease, or disease process. Vertebro-basilar artery syndrome results from transient insufficiency of vertebro-basilar artery blood flow. Because the vertebro-basilar arteries provide blood supply to the brain, the symptoms and signs associated with arterial insufficiency of these blood vessels are neurological in nature – this is the reason vertebro-basilar artery syndrome was reclassified to the nervous system chapter.


The vertebral arteries are paired arteries that rise from the right and left subclavian arteries. The vertebral arteries are divided into four parts, which include the prevertebral portion (V1), the cervical portion (V2), the atlantic or suboccipital portion (V3), and the intrancranial portion (V4). The basilar artery is formed by the right and left vertebral arteries, which unite in the base of the brain. The basilar artery joins with the internal carotid arteries at the base of the brain to form the circle of Willis. Together the vertebral and basilar arteries and their intracranial branches provide blood to the medulla, cerebellum, pons, midbrain, thalamus, and occipital cortex. Transient insufficiency of the vertebro-basilar blood supply results in symptoms and signs that are definitive for vertebro-basilar artery syndrome.

Neurological Symptoms and Signs of Vertebro-Basilar Artery Syndrome

A diagnosis of vertebro-basilar artery syndrome encompasses all the neurological symptoms and signs of vascular insufficiency and transient ischemia to the regions of the brain supplied with blood by the vertebral and basilar arteries and their branches. The most common symptoms include dizziness/vertigo, nausea and vomiting, changes in the level of consciousness, and headache. Other symptoms will vary depending on the exact site of the cerebral ischemia and may include hemiparesis/hemiplegia (which may alternate from one side of the body to the other), speech disturbances (dysarthria, dysphonia, etc.), visual disturbances (blurred vision, double vision, nystagmus, pupillary changes, visual field defects, etc.), sensory changes (paresthesias in the face and scalp, disturbances affecting pain and temperature sensation), and gait changes (ataxia). While the duration of the ischemic attack will vary, the defining characteristic of this diagnosis is that the neurological symptoms and signs are transient in nature. A loss of blood supply to the vertebral or basilar arteries resulting in cerebral infarction would not be reported with code G45.0.


Below is a table summarizing the classification and coding changes for transient cerebral ischemic attacks and related syndromes.

ICD-9-CM Code

ICD-10-CM Code

362.34 Transient arterial occlusion (retinal vascular occlusion)

G45.3 Amaurosis fugax

435.0 Basilar artery syndrome

435.1 Vertebral artery syndrome

435.3 Vertebrobasilar artery syndrome

G45.0 Vertebro-basilar artery syndrome

435.2 Subclavian steal syndrome

G45.8 Other transient cerebral ischemic attacks and related syndromes

435.8 Other specified transient ischemic attack

G45.1 Carotid artery syndrome (hemispheric)

G45.2 Multiple and bilateral precerebral artery syndromes

G45.8 Other transient cerebral ischemic attacks and related syndromes

435.9 Unspecified transient cerebral ischemia

G45.9 Transient cerebral ischemic attack, unspecified

437.7 Transient global amnesia

G45.4 Transient global amnesia

About the Author

Lauri Gray, RHIT, CPC, has worked in the health information management field for 30 years. She began her career as a health records supervisor in a multi-specialty clinic. Most recently she has worked as a clinical technical editor of coding and reimbursement print and electronic products. She has also taught medical coding at the College of Eastern Utah. Areas of expertise include: ICD-10-CM, ICD-10-PCS, ICD-9-CM diagnosis and procedure coding, physician coding and reimbursement, claims adjudication processes, third-party reimbursement, RBRVS and fee schedule development. She is a member of the American Academy of Professional Coders (AAPC) and the American Health Information Management Association (AHIMA).

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