Neuronal degeneration is seen in all of the following except:
D i.e. Neuropraxia Neuropraxia refers to physiological disruption of conduction only, no structural changes or degeneration occur. Neuronal degeneration is seen inQ - Crush nerve injury, Fetal development, Senescence Seddon's Classification of Nerve Injury Features Neuropraxia Axontemesis Neurontemesis Pathology - No anatomical disruption Axons & myelin sheath disrupted but - Complete division of nerve - Both axon & sheath intact - Physiological disruption of endoneural perineurium and epineurium sheath (neural tube) is - Axon & neural tube (i.e. perineurium, epineurium, & endoneural sheath) conduction only intactQ both are divided. Degeneration No degeneration Q Degeneration present proximal + distal Degeneration present proximal + Distal (Wallerian) (Wallerian) Neuroma No In continuity End or side neuroma Tinel's sign12/ Absent Advancing (present) Static Motor march Prognosis - Excellent - Good /fair /poor Poor - Recovery is complete usually with in 6 weeks - Occurs as regenerating axons grow into intact sheath - Electrodiagnostic studies (like nerve conduction study & EMG) are used to distinguish between paial & complete lesionQ and to establish a baseline for monitoring subsequent functional recoveryQ. However, these are not helpful until 2-3 weeks after an acute injury. - If a muscle lose its nerve supply (d/t nerve injury), EMG shows denervation potential at 3rd week; which exludes neuropraxia but however does not differentiate between axontmesis and neu rontemesis. All types of injuries may cause sensory, motor or both loss depending on type of nerve damaged. * Each axon is covered by myelin sheath (in myelinated nerve only) &/or neurilemma (Schwann sheath). Each nerve fiber (containing many axons) is covered by endoneurium. Each fasciculus (containing many nerve fibres) is covered by perineurium. And each nerve (containing mamy fasciculus) is covered by epineurium.
Crush nerve injury
Fetal development.
Senescence
Neuropraxia