Cerebrovascular disease can be caused by several processes involving cerebral and precerebral vessels: intrinsic (e.g., atherosclerosis, thrombosis, dissection); embolism from remote sites (primarily cardiac); decreased perfusion pressure; hyperviscosity; and vascular rupture (e.g., subarachnoid or intracerebral hemorrhage). Subdural hematoma is almost always due to trauma and is not classified as cerebrovascular disease.
A cerebrovascular accident (CVA) is a specific diagnosis defined by: 1) imaging that demonstrates acute cerebral infarction or hemorrhage, or 2) focal neurological dysfunction lasting 24 hours or more from onset, even in the absence of acute findings on imaging.
Keep in mind that patients often present after several hours of symptoms that are included in the duration. For example, a patient who presents with right hemiparesis for eight hours has had a CVA if the symptoms persist for another 16 hours or more. All neurological deficits, such as hemiparesis, aphasia, or ataxia, should be documented and coded.
A CT scan may not immediately demonstrate nonhemorrhagic CVA and is employed primarily to exclude hemorrhage. MRI is a much more sensitive test but occasionally remains unremarkable.
Complications like cerebral edema, brain compression, and coma should be documented when they occur. Simply stating that an imaging study shows midline shift or mass effect is inadequate for accurate code assignment, which should reflect the potentially life-threatening severity of these conditions.
A Glasgow Coma Scale (GCS) score should be recorded by nursing staff. A GCS of 8 or less is consistent with a diagnosis of coma; stupor, obtundation, or lethargy is usually used to describe patients with a higher GCS. Codes are assigned for each of the three component scores; do not code the total score. A code for the NIH Stroke Scale (NIHSS) may be assigned if desired but has no impact on diagnosis-related group (DRG) assignment.
In contrast to CVA, a transient ischemic attack (TIA) is a nonspecific description of a transient episode of focal neurological dysfunction that completely resolves within 24 hours in the absence of infarction or hemorrhage on imaging. TIA is really a symptom, and a confirmed or suspected underlying cause should always be documented following evaluation. For example, for a TIA with left hemiparesis and 40% occlusion of the right internal carotid artery, the diagnosis might be “suspected carotid stenosis as cause of TIA.”
Common causes of TIA include cerebral/precerebral stenosis and transient cerebral embolism from precerebral atherosclerotic plaque or remote sites, primarily cardiac. The finding of “noncritical” carotid stenosis (i.e., not requiring surgery) does not exclude transient embolism. Common cardiac causes of cerebral embolism include atrial fibrillation and valvular heart disease (especially when anticoagulant therapy is subtherapeutic), as well as cardiac mural thrombi, especially following myocardial infarction.
The term vertebrobasilar syndrome is problematic for coding and DRG assignment. The cause of the vertebrobasilar symptoms should be documented such as stenosis, occlusion, thrombosis, or embolism.
ICD-10-CM codes for CVA allow specificity of laterality and the affected artery (see Table). Coding of these specifics is desirable but not required for correct DRG assignment, since ICD-10-CM provides a code for unspecified CVA or “stroke.” Furthermore, clinicians do not have to document these specifics when CVA has been diagnosed, since they may be gleaned by coders from other medical record sources, such as imaging, without having to submit a query.
Code G45.9 is assigned for TIA; code G45.0 is used for vertebrobasilar syndrome. As principal diagnoses, both the codes are classified in the low-weighted symptom DRG 69 (TIA), which is targeted by recovery auditors for denial of inpatient level of care. However, codes for the underlying causes of these conditions—cerebral/precerebral stenosis, thrombosis, and embolism—are assigned to the higher-weighted DRGs 67 and 68, which are comparable to CVA DRGs and not targeted for medical necessity review.
In summary, CVA is recognized by imaging findings of acute infarction or hemorrhage and/or focal neurological dysfunction lasting 24 hours or more from onset. Identify and document comorbidities like cerebral edema, brain compression, and coma. TIA is defined by nonacute imaging and focal neurological dysfunction lasting less than 24 hours from onset. Always document the confirmed or suspected underlying cause of TIA symptoms, like cerebral or precerebral artery stenosis, transient cerebral embolism from precerebral arteries or distant sites like a fibrillating atrium, or an abnormal aortic or mitral valve.