Diagnosis and Management of Vertebrobasilar Insufficiency

Bow hunter’s syndrome successfully treated with a posterior surgical decompression approach: A case report and review of literature

BACKGROUND

Bow hunter’s syndrome (BHS) is a rare but surgically treatable cause of vertebrobasilar insufficiency due to dynamic rotational occlusion of the vertebral artery. Typically, patients present with posterior circulation transient ischaemic symptoms such as presyncope, syncope, vertigo, diplopia, and horizontal nystagmus, but irreversible deficits, including medullary and cerebellar infarctions, have also been described.

CASE SUMMARY

A 70-year-old patient presented an acute onset of vertigo and gait instability triggered by right head rotation. His medical history included previous episodes of unilateral left neck and occipital pain followed by light-headedness, sweating, and blurred vision when turning his head, and these episodes were associated with severe degenerative changes in the atlanto-dens and left atlanto-axial facet joints and right rotation of the C2 cervical vertebrae. Brain magnetic resonance imaging revealed the presence of acute bilateral cerebellar ischaemic lesions, while static vascular imaging did not reveal any vertebral artery abnormalities. Dynamic ultrasonography and angiography were performed and confirmed the presence of a dynamic occlusion of the vertebral artery V3-V4 segment when the head was rotated to the right secondary to left C1-C2 bone spur compression. Surgical decompression led to complete resolution of paroxysmal symptoms without neurological sequelae.

CONCLUSION

BHS should be considered in cases of repeated posterior circulation transient ischaemic attack or ischaemic stroke, particularly when associated with high cervical spine abnormalities.

Should we abandon positional testing for vertebrobasilar insufficiency?

Positional testing for vertebrobasilar insufficiency (VBI) is used by physiotherapists as part of pre-manipulative screening protocols. Recently, the validity of the tests have been questioned because a negative test does not infer safety with cervical manipulative therapy but the reasoning surrounding this opinion may be questioned. While the positional tests were developed to test vertebral artery flow contralateral to the direction of head movement and the subsequent effect on cerebral blood supply, as inferred by symptom reproduction, ultrasound studies have shown that vertebral artery flow is inherently variable. Rather, the tests should be considered as testing for adequacy of collateral flow in particular head positions rather than decreased blood flow in a particular artery, with more attention to characteristics of symptom reproduction. We contend that positional testing for VBI remains valuable for testing adequacy of collateral flow, and also has an important place as part of the differential diagnosis of individuals with dizziness or imbalance. The physiotherapist's ability to differentially diagnose dizziness and recognise the presence or not of VBI is not only critical for prompt medical investigation and management because it is a risk factor for transient ischaemic events and stroke, but has important influences over management decisions regarding cervical musculoskeletal treatment including exercise interventions. Importantly, the positional tests should not be considered as tests of arterial integrity and used to assess the risk of damage to the vertebral or internal carotid artery or presence of cervical arterial dissection. Urgent research is needed before we abandon positional testing prematurely.

The association between vertebrobasilar insufficiency and the risk of dementia: a nationwide register-based retrospective cohort study in Taiwan

OBJECTIVES

Neurodegenerative disorders are reportedly characterised by decreased regional cerebral blood flow. However, the association between vertebrobasilar insufficiency (VBI) and dementia remains unclear. In this nationwide, population-based, retrospective cohort study, we explored the potential association between VBI and dementia.

DESIGN

Nationwide population-based cohort study.

SETTING

Patients with VBI were newly diagnosed between 2000 and 2005 from the Taiwan National Health Insurance Research Database.

PARTICIPANTS

We included 3642 subjects as the VBI group. The control cohort included 14 568 randomly selected age-matched and sex-matched VBI-free individuals.

OUTCOME MEASURES

All subjects were followed until the diagnosis of dementia, death or the end of 2010. Patients with VBI, dementia (viz, vascular and non-vascular, including Alzheimer's) subtypes and other confounding factors were identified according to the International Classification of Diseases Clinical Modification Codes. Cox proportional hazards regression analysis was employed to examine adjusted HRs after adjusting for confounding factors.

RESULTS

Patients with VBI had a 1.807-fold (95% CI 1.643 to 1.988, p<0.001) higher risk to develop all-cause dementia than individuals without VBI. The risk was significantly higher in the VBI group than in the non-VBI group regardless of age (<65 years: HR: 2.997, 95% CI 1.451 to 6.454, p<0.001; ≥65 years: HR: 1.752, 95% CI 1.584 to 1.937, p<0.001). The VBI group had a higher risk of all-cause dementia than the non-VBI group regardless of sex and follow-up time intervals (<1 year, 1-2 years and≥2 years).

CONCLUSION

Patients with VBI appear to have an increased risk of developing dementia. Further research is needed to investigate the underlying pathophysiology.

Oxygen-glucose deprivation increases firing of unipolar brush cells and enhances spontaneous EPSCs in Purkinje cells in the vestibulo-cerebellum

Unipolar brush cells (UBCs) are excitatory interneurons in the granular layer of the cerebellar cortex, which are predominantly distributed in the vestibulo-cerebellar region. The unique firing properties and synaptic connections of UBCs may underlie lobular heterogeneity of excitability in the granular layer and the susceptibility to ischemia-induced excitotoxicity. In this study, we investigated the effects of oxygen-glucose deprivation (OGD) on the firing properties of UBCs and granule cells and spontaneous excitatory postsynaptic currents (sEPSCs) of Purkinje cells using whole-cell recordings. Short-term OGD induced increases in spontaneous firing of UBCs by causing membrane depolarization via the activation of NMDA receptors. UBC firing indirectly affected Purkinje cells by altering parallel fiber inputs of a subset granule cells, resulting in a marked increase in sEPSCs in Purkinje cells in vestibulo-cerebellar lobules IX-X, but not in lobules IV-VI, which have fewer UBCs. Similarly, the frequency and amplitude of sEPSCs in Purkinje cells were significantly greater in lobules IX-X than in IV-VI, even in control conditions. These results reveal that UBCs play key roles in regulating local excitability in the granular layer, resulting in lobular heterogeneity in the susceptibility to ischemic insult in the cerebellum.

The comparative analyses of the auditory evoked potentials and color Doppler sonography findings in patients diagnosed with vertebrobasilar insufficiency

Auditory evoked potentials (AEP) represent an electrophysiological method used in the diagnostics of pathological changes of the brainstem. Patients with vertebrobasilar insufficiency (VBI) show changes in the AEP-caused ischemia of the brain structures that generate their responses. The aim of the study was to determine the diagnostic significance and correlation among the findings of AEP in patients with VBI established by color Doppler sonography. The cross-sectional and prospective research included 48 inpatients and outpatients treated at the Clinic of Neurology, Clinical Center Nis. Ultrasound Doppler of blood vessels in the neck included an examination of the carotid blood vessels, the outcome and all sonographically available parts of the vertebral artery (VA) with particular emphasis on the intravertebral segment (V2). The morphological and hemodynamic characteristics of VA in this segment were monitored, and it was important to test the systolic velocity in two adjacent intervertebral spaces. Auditory evoked potentials were used to monitor the amplitudes, absolute latencies of waves I, II, III, IV, and V, as well as interwave latencies (IWLs) I-III, III-V, and I-V. There is statistically significant difference in the more frequent pathological finding of AEP in patients with higher degree of the reduced flow of VA established by color Doppler (P < 0.05) compared to patients with less reduction in the flow. Pathological findings of AEP are well correlated with pathological findings of VBI in color Doppler, and it may be applied as an additional and useful marker in diagnosis of VBI.