The Neurological echanism f Needle-Grasp in Acupuncture

C. C. Gunn, M.D., and W. E. Milbrandt, M.D. Clinical Research Unit, Rehabilitation Clinic Workers' Compensation Board, 5255 Heather St., Vancouver, B.C.• Canada

Abstract: The subjective appreciation of .. Teh minimal electrical stimulation - the motor Ch'iY> is probably related to the stimulation of nod­ point. It is now recognized that many acu­ ceptors, proprioceptors and interoceptors at the puncture points (Gunn's Type 1) correspond neurovascular hilus ("the motor point"). The ob­ jective component of Teh Ch'i Phenomenon con"'." to muscle motor points. 2 These deeper recep­ sists oflocal muscle spasm occurring at the point tors, unlike exteroceptors which respond to of stimulation. The needle is seen to be ..grasped" stimuli from the external environment, give or "sucked in." This paper discusses its possible rise to poorly localized sensation ofthe deep­ neurological basis. There are two types of needle­ seated variety. grasp-superjiclal and deep. The latter occurs only at Type I (motor point) acupuncture points within The objective component of the Teh Ch'i the ·muscle layer and is probably related to the Phenomenon consists of local muscle spasm gamma-loop. The functional characteristics of the occurring at the point of stimulation. The muscle spindle and the gamma-loop are reviewed., needle is seen to be "grasped" or "sucked In neuropathy and following denervation, the in".3 This needle-grasp may be occasionally phenomenon of .. denervation supersensitivity" develops. Muscles and peripheral receptors be­ so intense that some considerable tractive come supersensitive to transmitter substances and force has to be exerted to extract the needle to different forms of stimuli. When needle agita­ when it may be found to be bent (Fig. 1). tion occurs in a partially denervated or neuro-c What is the neurological basis of the needle­ pathic muscle, the intense local muscular contrac­ grasp? Why is it sometimes absent and some­ tion causes the needle-grasp and in extreme cases bending of the needle. Needle-grasp is usually most times present and so intense? obvious at tender motor points. Types of N eedle--Grasp

SoME NEUROPHYSJOLOGlCAL aspects of the Any experienced practitioner of acupunc­ subjective appreciation of .. Teh Ch'i" - a ture will be familiar with the two types of combined feeling of soreness, heaviness or needle-grasp. pressure, numbness, fullness or distention a) Superficial - this occurs when the needle have been previously discussed. 1 The vague has penetrated the skin for only a milli­ and ill-defined sensations are probably re­ meter or so. Upon rotation ofthe needle, lated to the stimulation of afferent fibers the skin around the needle contracts and arising from nociceptors, proprioceptors and when traction is applied to the needle, the interoceptors concentrated at the motor band skin puckers and is lifted by the needle of muscle near the neurovascular hilus · and point (Fig. 2). This superficial contraction deep to that area of skin most accessible to is distinct from the deeper variety ocur-

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65 ring in muscle and may occur at any point (cerebellum and cerebral cortex). The pro­ on the skin. The skin is composed of two prioceptors at musculotendinous junctions . layers of distinctive structural properties are the Golgi tendon receptors which :respond .. and embryological origin. The dermis or to changes in force o:r tension. They a:re re­ corium is a connective t.issue layer of sponsive only when a muscle contracts mesenchymal origin which is covered by against a load with their afferent input pro­ the epidermis, an epithelial layer derived portional to muscle tension regardless of from embryonic ectoderm. Deep to the muscle length. Their input excites inhibitory dermis lies a layer of loose irregular con­ intemeurons that synapse with motor neu­ nective tissue forming the superficial rcms controlling the same muscle. The pro­ fascia (hypodermis or subcutaneous prioceptors at muscle spindles are more layer), which in turn is bound to the complex and are relevant to the Teh Ch'i underlying tissues by a dense fibrous deep needle-grasp phenomenon. The muscle fascia corresponding to the epimysium spindle, about 3 millimeters in length, is en­ of muscle blocks (see Fig. 3). The dermis closed in connective tissue and is part of the gives the skin its mechanical strength by essential feedback mechanism by which virtue of the high proportion of collagen skeletal muscle is controlled (Fig. 4). Their · fibers intermingled with fibers of elastin. intrafusal fibers (as opposed to the extrafusal The superficial grasping of the needle is fibers of the rest of the muscle bulk) are in­ probably related to local contraction of nervated by gamma motor fibers originating these fibers of elastin. in the ventral horn and passing through the ventral root. (Extrafusal fibers are innervated b) Deep or Muscular- this deep needle­ by the alpha motor neurons). Afferent neu­ grasp occurs only at Type I (motor point) rons are from the primary endings or annulo­ acupuncture points within the muscle spiral endings wound around the intrafusal layer. Although the vague and ill-defined fibers. There are also secondary flower-spray subjective feeling of Teh Ch~i is a constant endings on both sides of the annulospiral finding when the needle is accurately endings. Both primary annulospiraJ. and placed in the neurovascular hilus, the ob­ secondary flower-spray endings are sensitive jective component only occurs under to stretch of the central portion of the spindle. certain circumstances (to be discussed). The afferent discharge of the spindle on the motor neurons of the same muscle is exita­ Musde Proprioceptors and the rory, thus, when a muscle is stretched, the Gamma-Loop spindle reflexively stimulate it to control and The proprioceptors in mammalian muscle resist stretch. Conversely, shortening of the consi~ts of the muscle spindle and the Golgi muscle favors relaxation. Through inter­ tendon organ. A review of the functional neurons and collaterals, spindle activity also characteristics of the muscle spindle and the determines the activity of antagonists and gamma loop is important for an understand­ synergists. The spindle is, in effect, the sen­ ing of the Teb Ch'i needle g:rasp.4 sory component of the muscle-stretch or Muscle and joint proprioceptors are re­ myotatic reflex - the same mechanism oper­ sponsible for signaling physical changes in a.tion in the so-called .. tendon reflex" tests. the musculoskeletal tissues. They are of three Stimulation of a hypersensitive spindle sen­ main categories and are related to joint posi­ sory mechanism leads to hyperexcitation of tion and motion, musde tension and muscle the same muscle and contributes towards. the length. Proprioceptors around joints (capsule muscle spasm seen in the Teh Ch'i Phenom­ and ligaments) are the Ruffini endings. They enon. (Agitation of the needle is specific do not have a selective influence via seg­ since these receptors are mechanoreceptors). mental relay pathways but influence postural The gamma-loop is sometimes viewed as the and locomotor patterns at higher centers "'automatic gain control" of the length-regu-

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66 Fig. 2 Fig. 1. Superficial (or skin) type of needle-grasp which Bent Needles Resulting from Deep Intense can occur at any skin point and is not necessarily "Needle-Grasp" of Teh Ch'i. associated with leh Ch'i. lating mechanism for each muscle. Disrup­ cles and peripheral receptors. These become tion of this mechanism with motor and other supersensitive to transmitter substances and dysfunctions is sometimes labeled as •4somatic to different forms of stimuli. In normal mus­ dysfunction" or the 6&osteopathic lesion",s cle, the muscle fiber membrane zone contain­ that is "a facilitated segment of the spinal cord ing receptor sites activated by acetycholine is maintained in that state by impulses of endo­ confined to that area immediately adjacent genous origin entering the corresponding to the end-plate, but following injury or after dorsal root. AU structures receiving efferent denervation the area sensitive to acetycholine nerve fibers from that segment are, therefore, spreads along the surface membrane until the potentially exposed to excessive ex.citation entire fiber responds to the agent. 6 A similar or inhibition." Since the central nervous increase in the number of receptors also system also has regulatory control, hyper­ occurs at autonomic and other synapses.4 sensitivity may occur in anxiety states and When an acupuncture needle is inserted into tension syndromes. normal muscle at a motor point, the afferent barrage via the primary Ia fibers and the Denervation Supersensitivity and monosynaptically relayed alpha efferent The Gamma-Loop message may yield a slight contraction of its homonymous muscle in the vicinity of the Muscle tonus is a state of continuous mild stimulating needle. However, when needle contraction of muscle dependent upon the agitation occurs in a partially denervated or integrity of the gamma-loop and their central neuropathic muscle (with hypersensitive connections. Atonic muscles are soft and receptors from denervation supersensitivity), flabby. Hypertonic muscles are rigid and the afferent barrage is increased. The result­ spastic. Normal muscle at rest has a certain ing magnified alpha efferent then initiates resilience rather than absolute flabbiness. intense local muscular contraction causing The maintenance and control of muscle tone the needle-grasp and in extreme cases bending is dependent upon the normal function at six the needle. The needle-grasp of the Teh Ch'i levels: (a) The precentral motor cortex., (b) the Phenomenon is usually most obvious at those basal ganglia, (c) the mid-brain, (d) the vesti­ motor points which are tender to palpation 1 bulum, (e) the spine, and (f) the neuromuscu­ since sensitivity of nociceptors is also height­ lar -system. ened following denervation. Similar positive In neuropathy and following denervation feedback mechanisms of hypersensitive noci­ there occurs a number of characteristics ceptor loops probably account for the ..Trig­ changes in the functional properties of mus- ger Points" of the myofascial syndrome.s

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67 ·Fig. 3. Schematic cross section of the histology of the skin. A IA. B - Epidermis. C - Dermis (rich with collagen and elastic fibers). D - Subcutaneous fat. E - Deep fascia. F - Muscle. G - Sµperficial nen'e plexus. H - Deep nerve plexus. J - Cutaneous nerve.

Fig. 4. Gamma Loop. A gamma (y) motoneuron is shown innervating the intrafusal muscle fibers of a muscle spindle. Excitation of gamma motoneurons by pathways, such as segmental reflex paths or tracts descending from the brain (indicated by the broken line ap­ proaching the gamma motoneuron cell body), will cause the contraction of the polar regions of mus~ cle spindles. This results in stretch of the equatorial regions of the spindles, with distortion of the affer. ent terminals belonging to group Ia fibers. The group Ia fibers that discharge will excite alpha (a) motoneurons to the same and to synergistic mus­ cles through the monosyna.ptic reflex pathway (and inhibit alpha motoneurons to the antagonist muscles). S. = SPHIDLE M "' MUSCLE FIBER

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68 Fig. S. Right-· Monopolar needle (electrode) as used in electromyography. Entire needle is teflon­ insulated except at the very tip. Left- Indifferent electrode used in conjunction with the above.

Electrodiagnostk Findings In our studies, a monopolar electrode is there is denervation or axonal degeneration. used. The monopolar electrode is constructed In mild neuropathy, the abnormalities in the from stainless steel wire sharpened to a point­ electromyogram · are not overwhelmingly ed tip and then insulated with Teflon except obvious but present as subtle changes from for the very tip (Fig. 5). Sterilization is by the normal state. s In our studies, we have autoclaving. The electrode is inserted into the observed that tenderness at a motor point muscle and a surface electrode is used as the and strong needle-grasp or local muscle con­ indifferent. Normal muscle at rest is electri­ tractions occur together and in varying cally silent, but at the motor zone of innerva­ degrees paralleling the electromyographic tion, end-plate "noise" may occur. This con­ findings of neuropathy. sists of miniature end-plate potentials (MEPP) which are non-propagated sub­ Summary threshold depolarizations. They may oc­ The ancient and well-known phenomenon casionally augment to evoke a propagated of .. Teh Ch'i" or ·~needle sensation" has both action potential in one or more muscle fibers. 9 subjective and objective aspects. The neuro­ End-plate noise is not a constant finding, but logical basis of the peculiar subjective sensa­ when it occurs, it is a good indication that the tion has been previously described. This needle tip is in the motor zone of innervation. paper discusses the probable neurological In neuropathy, electrodiagnostic findings are mechanism for the needle-grasp and postu­ related to (a) the presence of axonal failure, lates it to .relate. to the gamma-loop and (b) primary damage to myelin, (c) a combina­ muscle spindle. which may become hyper­ tion of both lesions and/ or (d) anterior horn excitatory in the presence of neuropathy and cell or neuronal disease. The electromyo­ denervation supersensitivity. graphic criteria of neuropathy9 include: Needle grasp is of two varieties: (a) Super­ an increase of insertion activity. a higher con-· ficial, and related to elastic connective tissue tent of polyphasic action potentials, a pro­ of dermis, and (b) deep and related to muscle. longation of the mean duration of motor unit The superficial variety occurs at all acupunc­ action potentials but with mean amplitude ture points but the deep variety occurs only normal or decreased and a partial inter­ at muscle motor points or Type I acupuncture ference pattern obtained despite maximal points. Intense needle-grasp is not a constant voluntary effort. Abnormal spontaneous finding and is probably present only when activity such as fibrillations, fasciculations the muscle spindle is hyperexitatory as in and positive sharp waves may appear when· neuropathy or partial denervation.

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69 References

l. Gunn, C. C., and Mildbrandt, W. E.: Trans­ 1973. pp. 51, 59,.103-108, 77. cutaneous Neural Stimulation, Needle Acu­ S. Korr, I. M.: Proprioceptors and Somatic Dys­ puncture and "Teh Ch'i" Phenomenon. Am. J. function. Journal A. O.A., Vol. 74, March Acupunclflre, Vol. 4, No. 4, Oct.-Dec. 1976, 1975, pp. 638/ 123-650/ 135. p. 317-322. 6. Axelsson, J., Thesleff, S.: A Study of Super­ 2. Gunn, C. C., Ditchbum, F. G., King, M. H .• sensitivity in Denervated Mammalian Skeletal Renwick, G. J.: Acupuncture Loci: A Proposal Muscle. J. Physiol., 147:178-193, 19.59. for Their Classification According to Their Relationship to Known Neural Structures. 7. Gunn, C. C., Milbrandt, W. E.: Tenderness at Am. J. Chin. Med., Vol. 4, No. 2, 1976, p. 183- Motor Points. J. Bone & Joint Surgery, Vol. 195. 58-A, No. 6, Sept. 1976, pp. 815-825. 3. Ministry of Public Health, People's Republic 8. Gunn, C. C.: Some Observations on the Nature of China: Acupuncture Anesthesia (Translation of Trigger Points. Osteophmic Physician, of a Chinese Publication of the same title). March 1977. U. S. Directory Service, 1975, p. 293-297. 9. Goodgold, J., Eberstemn, A.: Electrodiagnosis 4. Willis, Jr., W. D., and Grossman, R. G.: Medi- of Neuromuscular Diseases. The Williams & . cal Neurobiology. The C. V. Mosby Company, Wilkins Company, 1973, pp. 62, 164.

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