Two Chinese Patients With Vertebrobasilar Dolichoectasia
To the Editor:
We read with great interest the article, “Posterior Circulation Infarcts in Patients With Vertebrobasilar Dolichoectasia,” by Passero and Filosomi.1 We would like to make the following comments and describe 2 Chinese patients with vertebrobasilar dolichoectasia (VBD) who presented with features of vertebrobasilar stroke. (There is a minor printing mistake in Table 1 of the article, since 12 patients instead of 11 had prior transient ischemic attacks.1)
First, the authors suggested the following 2 pathophysiological mechanisms of infarction in patients with VBD: (1) infarcts in distal territories (including posterior cerebral artery territory) associated with artery-to-artery embolism and (2) brain stem/cerebellar infarcts associated with branch atheromatous disease. Nevertheless, the authors postulated in the following paragraph that slow flow and distortion were related to infarcts in the posterior cerebral artery territory and that infratentorial infarcts were related to distortion and stretching of the branches of the basilar artery. Finally, the authors also pointed out the importance of superimposed atheromatous changes in precipitating ischemia in pateints with VBD. Thus, we remain confused as to the most likely pathophysiological mechanisms for ischemia in VBD.
Second, VBD is an uncommon vascular anomaly, but the authors were able to study 40 consecutive stroke patients with associated VBD and compare them with another 40 VBD patients without stroke.1 We are interested in knowing the frequencies of VBD in both stroke patients and patients without stroke. In addition, we would like to know how the authors collected the 40 VBD patients without stroke. Was the diagnosis of VBD made in postmortem examinations? If the VBD was diagnosed by (CT) or MRI, what were the presenting symptoms and why were neuroimaging tests indicated?
The Queen Mary Hospital of Hong Kong is a regional hospital serving a population of one-half million. Stroke patients are routinely assessed by a member of the Division of Neurology, who collects prospective data for our stroke database and recommends appropriate management. Our stroke database has collected information from 358 stroke patients between January 1997 and May 1998, and ischemic stroke affected 275 of these patients. Brain stem/cerebellar infarctions occurred in 25 patients. During this period, we have encountered 2 Chinese patients with VBD. The first was a 73-year-old hypertensive woman who had postradioiodine hypothyroidism on replacement therapy. She presented with sudden onset of right-sided weakness and numbness, dysarthria, dysphagia, and vertigo. Initial examination showed normal consciousness, horizontal nystagmus, left sixth nerve palsy, dense right hemiplegia, and right upgoing plantar response. CT of the brain revealed calcified VBD and possible left pontine infarct. MRI and MR angiography confirmed VBD with possible dissection, extensive brain stem infarct, and asymptomatic right middle cerebral artery aneurysmal dilatation. She was given subcutaneous injections of low-molecular-weight heparin. Her consciousness deteriorated during the first few days, but her condition later improved. She survived with significant neurological deficits.
A 75-year-old woman with history of hypertension and diabetes mellitus presented with progressive slurring of speech and limb weakness for 10 days. Initial examination revealed dysarthria, left-sided hypertonus, mild generalized weakness, and ataxia of both arms. CT showed calcified VBD only. She became confused, with agitation, over the next 2 days and had 2 episodes of generalized tonic-clonic convulsions on day 3 after admission. Repeat CT showed no interval change, and treatment with phenytoin was commenced. Her consciousness deteriorated further, and she became unresponsive following 2 more episodes of generalized seizures. Her seizure did not recur after add-on therapy with sodium valproate. When neurological examination was repeated, we found that the withdrawal response to noxious stimuli was impaired on her left side and her gaze was deviated to the left. Thus, our diagnosis was evolving brain stem infarction related to her VBD. MRI of her brain was performed 3 weeks later. Although the VBD was confirmed, MRI did not show any infarction in her brain. Follow-up EEG revealed periodic, 1-Hz generalized sharp waves typical of Creutzfeldt-Jakob encephalopathy. Her cerebrospinal fluid was normal. She was subsequently sent to a convalescent hospital for long-term care. These 2 cases illustrate the fact that stroke associated with VBD is uncommon (1 in 25 patients with brain stem/cerebellar infarcts) in Chinese and that VBD or other aneurysmal arterial dilatation may be an incidental finding unrelated to the neurological symptoms.
References
- 1 Passero S, Filosomi G. Posterior circulation infarcts in patients with vertebrobasilar dolichoectasia. Stroke.1998; 29:653–659.CrossrefMedlineGoogle Scholar
We thank Drs Cheung and Mak for their interest in our article, and we regret the printing error in Table 1. It is impossible to name the “most likely pathophysiological mechanisms for ischemia in VBD.” Several mechanism may be involved, and every patient has different features related to the degree of ectasia, vertical elongation, and lateral displacement of the basilar artery and to the presence of atheromatous changes of the posterior circulation. Common mechanisms (arteriolar lipohyalinosis, obstruction by atheroma or intraluminal thrombus, and artery-to-artery embolism) may be operating, and some have been regarded as being responsible for ischemia associated with VBD.R1R2R3R4R5R6 Our patients may be classified according to classic criteria and assigned to one of these mechanisms.
Because in VBD other specific mechanisms such as distortion of branches of the basilar artery (BA) and hemodynamic factors may contribute to ischemia,R5R7 we analyzed some aspects of the BA (degree of ectasia, vertical elongation, and lateral displacement). The results of this analysis showed that location of infarcts was linked to some characteristics of the BA, which suggests certain pathophysiological mechanisms (reduced blood flow velocity and possible distortion of the posterior cerebral arteries and their small branches, and distortion and/or stretching of the branches of the BA).
The importance of superimposed atheromatous changes in precipitating ischemia in patients with VBD emerges from a comparison of VBD patients with and without stroke. Ischemic complications of VBD were more often observed in patients who had superimposed atheromatous changes of the posterior circulation.
In conclusion, (1) the presence of atheromatous changes of the posterior circulation, with its consequences (artery-to-artery embolism, branch atheromatous disease) is an important factor for ischemic complications in VBD patients but not a necessary condition, since some patients with stroke had no atheromatous changes; and (2) pathophysiological mechanisms closely linked to the characteristics of the BA operate in VBD patients with ischemic complications together with any atheromatous changes.
VBD is regarded as “uncommon” and often asymptomatic, and many papers on the topic, including mine,R8R9 open with this premise. Actually, the true incidence of VBD and the frequency with which this vascular anomaly becomes symptomatic are still uncertain. Being infrequent, the means used to detect it and the type of patients investigated are important. The most suitable means are undoubtedly MRI and MR angiography. In our experience and that of others,R10 CT scan may not be sufficient. With regard to the type of patient, if we look for VBD in populations at risk (ie, patients with vertebrobasilar ischemia, hemifacial spasm, cranial nerve syndromes, auditory-vestibular symptoms, and trigeminal neuralgia), we have a greater probability of finding patients with this anomaly. We recently found a close association between VBD and idiopathic bilateral vestibular loss.R11 On this point the literature is clear: in studies of patients who underwent cerebral angiography, the incidence of VBD ranged from 0.17% to 5.8%12–14; in selected series of patients, the rates of VBD were 2% to 7% in patients with trigeminal neuralgia,R15R16 4.8% in patients with cranial nerve syndromes,R17 2.5% in patients with lateral medullaryR18 or thalamicR19 infarcts, 2.8% in patients with pontine infarcts,R20 3.3% in patients with cerebellar infarcts,R21 7.1% in patients with lower brain stem infarcts,R22 12.5% to 14.3% in patients with vertebrobasilar infarcts,R23R24 26.7% in patients with vertigo and slowing of vertebrobasilar flow,R25 and 78.3% in patients with hemifacial spasm.R26
We began gathering our population in 1980 in collaboration with the Institutes of Radiology, Otolaryngology and Neurosurgery. We created a type of VBD register for the pupose of studying clinical and imaging data and, in particular, follow-up. Our register now includes 124 patients who on the basis of clinical presentation may be grouped as follows: 47 with acute cerebrovascular ischemic events (transient ischemic attack or stroke), 17 with intracerebral hemorrhage (ICH), 39 with cranial nerve syndromes and/or auditory-vestibular symptoms, 2 with hydrocephalus, and 19 with incidental VBD. It is difficult to evaluate the epidemiology; however, patients with cerebrovascular ischemic events belong to a series of approximately 6300 patients hospitalized for acute cerebrovascular ischemic disease; those with ICH belong to a series of 1005 patients with ICH; and patients with other types of presentation were among those hospitalized in our institute or in the Institute of Otolaryngology and those seen in the respective outpatient clinics. For patients with cerebral ischemic or hemorrhagic events, the incidence of VBD (0.75% and 1.7%, respectively) can be calculated since all did at least CT scan. It cannot be calculated for other patients because not all of them did imaging studies.
As clearly stated in our article, all patients were diagnosed by CT scan, cerebral angiography, or MRI studies, and not by autopsy. Of our 40 VBD patients without stroke, 14 had impairment of one or more cranial nerves, associated in 8 with auditory-vestibular symptoms; 11 had vestibular symptoms (imbalance, vertigo, oscillopsia); 2 had auditory symptoms (tinnitus and hearing loss); 3 had combined auditory and vestibular symptoms; and 10 had symptoms unrelated to the VBD. Patients with cranial nerve impairment had involvement of the facial nerve (paresis with nuclear/peripheral pattern or hemifacial spasm; n=5), trigeminal nerve (neuralgia or sensory disturbances with peripheral pattern; n=4), or both (n=5). Additional cranial nerves were involved in 3 cases. In patients with cranial nerve syndromes or with auditory-vestibular symptoms, the need for imaging is evident and requires no further comment.
Drs Cheung and Mak found 1 case of VBD among 25 patients with brain stem/cerebellar infarcts (4%) or 2 cases among 275 stroke or presumed stroke patients (0.72%). These percentages are in line with the above, and it may be premature to suggest that VBD is rarer in Chinese patients. It is incidental and well known that VBD may be asymptomatic or unrelated to the neurological symptoms.R11R13R15R27
