Severe pain which arise after injury to or sectioning of a peripheral sensory nerve is called as:
Complex Regional  Pain Syndrome (Causalgia, Reflex Sympathetic Dystrophy Syndrome)
Causalgia is a term applied to severe pain which arises after injury to or sectioning of a peripheral sensory nerve. 
Although few reports of this condition exist in the dental literature, cases do occur after the extraction of teeth. It has readily identifiable signs and symptoms and is treatable if recognized early; however, the syndrome may become disabling if unrecognized.
Key Concept:
Causalgia manifests as severe pain after injury or sectioning of a peripheral sensory nerve following a diﬃcult extraction. The other names are complex regional pain syndrome and reﬂex sympathetic dystrophy syndrome.
Reference: Shafer’s Textbook of ORAL PATHOLOGY Eighth Edition page no 578
Temporal arteritis
Neuralgia
Neuritis
Causalgia