The main symptoms of inadequate blood supply to the basilar artery are: 1. diplopia, which refers to double vision when looking at things with both eyes. 2. dysarthria, which means the inability to produce normal speech and sound, and difficulty swallowing. 3. vertigo and ataxia, which means difficulty maintaining balance when walking and falling easily. 3. ipsilateral hemianopia, which means the eye appears black when looking to one side and cannot see the visual field. 4. ipsilateral hemianopia, which means the eye has no visual field when looking to one side or the other. 5. 5.Sudden collapse attack, sudden collapse, impaired consciousness, or motor and sensory impairment.