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INSUFFICIENCY. What is not competent; not enough.

A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.
References in periodicals archive ?
Do not diagnose vertebrobasilar insufficiency. Chinese Stroke Neurol Dis.
Comparison of vertebral artery velocity and flow volume measurements for diagnosis of vertebrobasilar insufficiency using color duplex sonography.
Drop attacks; falls; vertebrobasilar insufficiency; geriatrics; aged; drug therapy.
Because of the prevalence of cerebrovascular disease and the reported association of drop attacks with neck hyperextension and with abnormalities of the brain stem, vertebrobasilar insufficiency is generally considered to be a common cause of true drop attacks in the elderly.[24] Drop attacks have been reported to occur in up to 25% of patients with symptomatic vertebrobasilar insufficiency.[25] In such cases, the pathophysiologic mechanisms may include mechanical obstruction (kinking) of the vertebrobasilar arteries,[26] sudden systemic hypotension (caused by arrhythmia, for example), embolization, or spasm.
In experimentally induced vertebrobasilar insufficiency in both rabbits and dogs, Hirschberg and Hofferberth[43] have demonstrated a beneficial effect of calcium channel blockers on ischemia-induced vestibular nystagmus.
The relatively high incidence of its occurrence suggests that this condition may be of significance in the cause of vertebrobasilar insufficiency as it may cause external pressure on the vertebral artery as it passes from the foramen transversarium of the atlas vertebra to the foramen magnum of the skull reducing its cross sectional area and compromising its blood flow.
However, these lesions produce neurologic symptoms when compensatory flow to the subclavian artery from the vertebral artery diverts too much flow toward the arm and away from intra-cranial structures leading to vertebrobasilar insufficiency (VBI) (1) for example during arm swinging.
This results in a steal blood phenomenon at the expense of the basilar artery, as blood flow is reversed to the ipsilateral occlusion VA, which leads to a hypoperfusion state in the vertebrobasilar arterial (VBA) system and thus vertebrobasilar insufficiency (VBI).
Vertigo and vertebrobasilar insufficiency. ActaOtolaryngol (Stockh) 1988;460:128-34.