My mother is 39 years old. For the past few months, she has been having repeated episodes where first she feels mild water/saliva coming into her mouth. After that, she starts getting a headache. Then she feels anxiety/restlessness and pain in her face and throat. After this, her heartbeat becomes fast. During these episodes, she is unable to speak properly, only some sound comes out. We have checked her blood pressure many times and it is always normal. This problem happens mostly during cold weather. Please guide us about the possible cause and treatment.