Neurophysiological Effects of Latent Trigger Point Dry Needling on Spinal Reflexes.

Abstract

Deep dry needling (DDN) is a method to treat muscle trigger points (TrPs) often found in persons with neuromuscular pain and spasticity. Currently, its neurophysiological actions are not well established. Thus, to understand how DDN affects spinal cord physiology, we investigated the effects of TrP DDN on spinal reflexes. In 17 adults with latent TrPs in the medial gastrocnemius (MG) without known neurological or orthopedic injuries, the H-reflex, M-wave, and reciprocal inhibition in the soleus, MG and lateral gastrocnemius (LG), and passive ankle range of motion (ROM) were measured before and immediately after, 90 minutes, and 72 hours after a single bout of DDN at the MG TrPs. The MG maximum M-wave (M_max) amplitude was decreased at immediately and 90 minutes post DDN (by -14 and -18%) and returned to pre DDN level at 72 hours post. LG and soleus M_max did not change. The maximum H-reflex (H_max) amplitude did not change in any of the triceps surae. Soleus inhibition was increased significantly at immediately (+30%) and 72 hours post DDN (+36%). ROM was increased by ≈4 deg immediately and ≈3 deg at 72 hours post DDN. Temporary reduction of MG (but not soleus or LG) M_max amplitude after DDN and its recovery at 72hours post indicates temporary and specific effects of DDN in the treated muscle. The immediate and 72 hours post increases in the ROM and soleus inhibition with no changes in H_max suggest complex effects of DDN at the spinal level.