There are many patients with dizziness/vertigo in neurology clinics and doctors tend to make certain mistakes in the process of diagnosis, which are summarized in two categories of mistakes. The first mistake is to attribute the main cause of dizziness/vertigo to the now obsolete name of vertebrobasilar artery insufficiency of blood supply, and the second mistake is to assume that certain abnormal test results are the cause of dizziness/vertigo or the cause of cerebral insufficiency of blood supply. These patients are not only seen in neurology but may also be seen in ENT. Otologists who are unaware of the above mistakes made by neurologists, when they see a patient diagnosed with VBI in neurology, mistakenly assume that this patient has VBI and even influence the diagnostic thinking of some otologists, are making a big mistake. Of course there are other diagnostic misconceptions that we neurologists should try to avoid, and otologists should also pay attention to.
I. VBI has been renamed as posterior circulation ischemia
In 2006, the expert consensus on posterior circulation ischemia in China elaborated the process of international understanding of PCI. In 2000, Professor Caplan, an international authority on stroke, suggested the term “PCI”.
So, how is dizziness/vertigo diagnosed as VBI in a large number of middle-aged and elderly people in China? The diagnosis is made with the help of cervical spine radiographs and transcranial Doppler ultrasound. A state that is both abnormal and does not meet ischemic criteria is difficult to define clinically, and both of these adjunctive tests are highly problematic for diagnosing VBI or PCI.
II. Cervical spondylolisthesis is not a major cause of PCI
A significant proportion of dizziness/vertigo patients seen in outpatient clinics have had cervical-X-rays taken, especially in the elderly. The diagnoses that often appear on cervical spine X-ray reports include straightening of the cervical curvature, narrowing of the vertebral space, and osteophytes, etc. These patients themselves ask, “Doctor, is my lack of blood supply to the brain caused by cervical spondylosis?”
The cervical spine osteophytes are not the main cause of posterior circulation ischemia, and there is no difference in the degree of osteophytes among elderly people with VBI at the same age, therefore, cervical spondylosis is not the main cause of PCI. However, most patients with osteophytes cannot explain their dizziness/vertigo. Therefore, for elderly people with osteophytes on cervical spine X-rays, their dizziness/vertigo should also be carefully analyzed to avoid missing the real cause of PCI or the more common benign positional vertigo or psychosomatic disorders.
III. TCD cannot diagnose cerebral insufficiency
A significant proportion of dizziness/vertigo patients seen in outpatient clinics have also had TCD. Patients often have been suffering from dizziness/vertigo for a long time, and the first thing they say when they sit down is “Doctor, I am dizzy”, and the second thing they say is “I have cerebral blood supply deficiency”. Then he would take out the TCD report from his bag, and it often says “insufficient blood supply to the vertebrobasilar artery”, and with such a report, the patient cannot believe that he has insufficient blood supply.
So, can TCD diagnose cerebral insufficiency? The answer is clear, no. But the trouble is that many neurologists do not know that TCD cannot diagnose cerebral insufficiency, and when they see a TCD report like this, they think that TCD can diagnose cerebral insufficiency, and the more serious problem is that the operator who writes the TCD report of cerebral insufficiency does not know that TCD cannot diagnose cerebral insufficiency, and if he knew this, the technician would not make the diagnosis in this way. We are actively correcting these errors in neurology and among TCD operators, but there is still a long way to go. I will briefly explain why TCD does not diagnose cerebral hypoperfusion.
TCD detects blood flow through a vessel by ultrasound and knows the speed of blood flow by calculating the frequency shift between the received ultrasound and the emitted ultrasound. An erroneous TCD diagnostic report is one in which the operator diagnoses cerebral insufficiency based on the detected slowing of blood flow. However, blood flow velocity and blood flow through the vessel are two different concepts. The unit of velocity is cm/s, which is the distance flowed per unit time, while the unit of flow is ml/s, which is the volume flowed per unit time, and the area must be available when calculating the volume. However, TCD can only detect the velocity, but not the flow. For example, for the same blood flow rate, if the diameter of the artery is different, then the flow rate through this artery must be different, with a large flow rate for a thick diameter and a small flow rate for a thin diameter. Therefore, without knowing the diameter of the artery, the value of blood flow velocity detected by TCD is not equal to the amount of blood flow through the artery, i.e., a slowed blood flow velocity cannot be diagnosed as insufficient blood supply. The decrease in flow velocity on review is due to the fact that the diameter of the stenosis has thickened, so although the flow velocity has decreased, the amount of blood flowing through it has increased. The reason is so simple: high or low blood flow velocity is not equal to more or less blood flow through this artery, so TCD cannot diagnose cerebral insufficiency based on the change of blood flow velocity.
IV. Lacunar infarcts or ischemic lesions do not cause cerebral insufficiency
As we know from the previous two subsections, cervical spine osteophytes in the elderly are usually not the cause of dizziness/vertigo or PCI in patients, and TCD cannot diagnose cerebral insufficiency based on blood flow velocity alone. Therefore, the above two diagnoses most often used by neurologists to explain dizziness/vertigo in patients are not reliable or are speculation or conjecture by neurologists without definite evidence.
There is also a brief mention here about lacunar infarction and cerebral hypoperfusion. A phenomenon very similar to the one mentioned in the previous section is that the first thing a patient says when he or she is seen is “I’m dizzy, doctor,” and the second thing he or she may say is “I have a lacunar infarction. Then he or she will be eager to take out the cranial CT film and show it to the doctor. The patient’s meaning is clear: my dizziness is caused by cavernous infarction in the brain, so doctor, see how to treat my dizziness by treating my cavernous infarction. And the patient will also tell me that he has been receiving fluids locally for many days, but they are not effective. It is not surprising that an elderly person with one or more of the risk factors such as hypertension, hyperlipidemia, diabetes or smoking has a few small foci of infarction or ischemia due to small arterial lesions on a cranial CT or magnetic resonance imaging (MRI), but these small foci of infarction or ischemia are not related to the patient’s dizziness/vertigo symptoms and do not cause inadequate blood supply to the brain. Therefore, otolaryngologists should not worry about whether this patient has dizziness caused by cerebral insufficiency when they see a cranial CT report or a cranial MRI report with lacunar infarcts or ischemic lesions; there is no necessary connection between them.
V. Relationship between cerebral artery stenosis and PCI and clinical manifestations of PCI
Modern imaging technology is developing very fast, including imaging technology for the diagnosis of cerebrovascular lesions. Some patients with dizziness/vertigo may have had one or more of the following tests, such as carotid ultrasound, TCD, magnetic resonance angiography, CT angiography, or digital subtraction angiography, and some patients with stenosis or occlusion in one or more of the above tests, are these arterial stenoses related to the patient’s dizziness/vertigo? Or is the patient’s dizziness/vertigo caused by insufficient blood supply due to cerebral artery stenosis? Clinically, we neurologists also encounter many such cases that need to be determined.
The cerebral circulatory system has an anterior circulation and a posterior circulation. The anterior circulation arteries include the internal carotid artery, middle cerebral artery and anterior cerebral artery. In the case of stenosis or occlusion of the middle or anterior cerebral artery, dizziness/vertigo is usually not present, so even if a patient is found to have an occlusive lesion of the middle or anterior cerebral artery by one of the tests mentioned above, it is not considered to be related to the patient’s dizziness/vertigo. After severe stenosis or occlusion of the internal carotid artery, it is possible for a patient to have symptoms of PCI if there is a posterior to anterior collateral branch compensator present. The major arteries of the posterior circulation include mainly the vertebral, basilar and posterior cerebral arteries. Patients with severe stenosis or occlusion of the vertebral and basilar arteries are at risk for PCI, which means that it may be the cause of the patient’s dizziness/vertigo.
If a patient with dizziness/vertigo is found to have severe stenosis or occlusion of a major artery of the posterior circulation by the above mentioned tests, is that the cause of this patient? No. Common symptoms of PCI include, in addition to dizziness/vertigo, symptoms of brainstem or cerebellar damage, such as numbness of the head and face, numbness or weakness of the limbs, diplopia, transient loss of consciousness, unsteadiness in walking or falling. The corresponding signs of brainstem or cerebellar damage may be detected during physical examination. Dizziness/vertigo alone is rare in patients with PCI and is often accompanied by other signs and symptoms. Therefore, even if this patient with dizziness/vertigo is found to have cerebral artery stenosis in the posterior circulation, it is not certain that it is necessarily the cause of this patient’s dizziness/vertigo.
VI. The main cause of dizziness/vertigo is not PCI
At this point, the thoughtful reader must have realized that it is not so easy for us to diagnose a patient with dizziness/vertigo who comes to our neurology clinic with PCI or VBI. Cervical spine osteophytes are not, TCD diagnosis of inadequate blood supply is not correct, brain CT or MRI with lacunar infarcts or ischemic foci is not, anterior circulation artery stenosis or occlusion is not, and even if stenosis or occlusion of the posterior circulation aorta is found it is not necessarily the case, so, PCI is rarely? Whether in neurology, otology, general practice or dizziness specialty clinics, vestibular central etiology accounts for less than 10% of all cases, and not all of the vestibular central lesions are PCI, thus showing that PCI is definitely not a major or common cause of outpatient dizziness or vertigo. As a neurologist, you should never easily give a diagnosis of PCI or VBI to a patient, because a diagnosis of VBI not only hides the real cause of the patient, such as BPPV, but also makes the patient’s mental and psychological burden heavier and heavier because the patient is not diagnosed and treated for a long time, so that the dizziness/vertigo symptoms will not be cured.
VII. The main cause of PCI is atherosclerotic stenosis of large arteries
PCI refers to posterior circulation infarction and TIA, and its etiological diagnosis follows the etiological diagnosis of TOAST staging that we usually talk about, including cardiogenic embolism, atherosclerotic large arteries, occlusion of small penetrating arteries, other etiologies and etiology unknown. Therefore, patients with a suspected PCI should be scheduled for appropriate testing and etiologic classification according to ischemic stroke before the most appropriate treatment can be given. In the analysis of 407 cases of posterior circulation infarction in the New England Medical Center posterior circulation registry, atherosclerotic in large arteries accounted for about 50%, cardiogenic for 20-30%, small arterial occlusion in penetrating branches for about 15%, and other etiologies for 10-15%. It can be seen that the main etiology of PCI is atherosclerotic stenosis of large arteries.
VIII. Diagnosis of posterior circulation cerebral artery stenosis
As mentioned earlier, there are many methods to diagnose cerebral artery stenosis, so is it possible regardless of which method is used? Of course, if the patient has a DSA, then the vasculature can be seen most clearly, but most outpatients with suspected PCI will not have a DSA examination because DSA is invasive and requires hospitalization. More outpatients with suspected PCI choose non-invasive or minimally invasive vascular imaging, including carotid ultrasound, TCD, MRA and CTA. carotid ultrasound is highly accurate in diagnosing stenosis of the common carotid artery, internal carotid artery, external carotid artery and subclavian artery, but many hospitals are still unable to diagnose stenosis at the beginning of the vertebral artery or have poor accuracy, which is TCD can diagnose intracranial and extracranial aortic stenosis, including anterior and posterior circulation, through changes in blood flow velocity and spectral pattern, but TCD has a high rate of missing stenosis and occlusion of vertebral and basilar arteries, which is related to the tortuous course of vertebral and basilar arteries and the operator’s technique. This is related to the tortuosity of the vertebral and basilar arteries and to the operator’s technique; therefore, in most hospitals, TCD does not exclude vertebral or basilar artery stenosis or occlusion even if the report is normal. Conventional MRA can only examine the intracranial arteries. Enhanced MRA and CTA are able to examine intracranial and extracranial arteries completely. CTA can observe not only whether there is stenosis in the artery, but also whether cervical spine osteophytes are compressing the vertebral artery. The amount and intensity of information provided by different diagnostic methods for cerebral artery lesions varies, and we must be very careful when analyzing vascular imaging results.