Intervertebral Disc Pathology and Ayurveda
An intervertebral disc or intervertebral fibrous cartilage lies between adjacent vertebras in the vertebral column. Each disc forms a fibrous cartilaginous joint (a symphysis) to allow slight movement of the vertebra and acts as a ligament to hold the vertebra together. Their role as shock absorbing in the spine is crucial. Intervertebral disc disorder is a condition that involves deterioration, herniation or other dysfunction of an intervertebral disc. The symptoms of intervertebral disc disorders such as low back pain are the ready cause of activity limitation and work absence throughout much of the world, imposing a high economic burden on individuals, families, community industries and governments2.
Intervertebral disc and its impact on aging:
In Ayurveda, there are two types of dhatu, i.e. stay and poshakadhatu.Asthi or bone can be considered as sthayidhatu and not the asthidhatu completely. Asthidhatu exists in liquid form called as poshakaasthi that traverse through the asthivahasrotas and nourishes the sthayiasthidhatu. From the contemporary science, the nutrients that are responsible for the nourishment of the bone tissue such as calcium, phosphorus, magnesium etc. can be considered as the poshakaasthidhatu. Overlooking embryological development of axial endoskeleton, first a notochord and then a vertebral column is the basic feature of chordate and their subphylum, the vertebrate, including mankind. A stiff but flexible axis, in bilaterally symmetrical animals that show an early tendency to elongation, prevents telescoping of the body during waves of contraction in successive segmental muscles to produce the sinuous movements, especially in the tail, which are the basic mode of locomotion in aquatic vertebrates. A chain of bones connected by discs of deformable substance develop around and largely replaced the notochord. However, notochordal vestiges occur in vertebrae of many fish, amphibians, and reptiles and centrally in mammalian intervertebral discs. This replacement is repeated in early vertebrate embryo10. Hence, the intervertebral disc can be included under asthidhatu. Asthidhatu can precisely be termed as the edifice bars, on the systematic framework of which human being stand. Therefore,asthidhatu facilitates dharana11. Here, asthidhatu can be understood as both vertebrae as well as the intervertebral disc. Based on the principal of ahrayaashrayibhava, vatadosha is inversely related to asthidhatu. Vatadosha increases physiologically with escalating age or in the old age12. Therefore age-induced degenerative changes to intervertebral discs are inevitable. There will be a significant reduction of kaphadosha with predominant apmahabhoota due to the rookshaguna13 induced by vatadosha predominant with akasha and vayumahabhoota14. Degenerative type of pathological conditions in the human body can be understood under the category of vata vyadhi. One among the condition affecting the sandhi byvata dosha – sandhigata vata is included under it. The term gata is derived from the root “gam” which means gone to,arrived at, situated in, directed to, hence, it can be revealed that the word gata is related with site (here asthi and sandi), in which vitiated vata dosha get lodged and manifest symptoms of asthi and sandhigata vata. In this condition due to exposure to etiological factors, aggravated vata accumulates in rikta srotas to give rise to various generalized and localized diseases. Here, in this context vata dosha is vitiated in vertebral joints (especially intervertebral disc), it leads to sandhigata vata. One among the common manifestation of intervertebral disc pathology is gridrasi. Gridrasi is a disease having its origin in pakwashaya and seat as sphik and kati i.e. lumbar spine. Cardinal features include distribution of pain that begins in the back and radiates through the posterior aspect of the thigh and calf to outer foot. Herniation and degeneration of the disc are the commonest causes.
Vatadoshaprakopakarana and lakshana with reference to asthi (vertebra and intervertebral disc):
Consumption of etiologies like tikta (bitter),kashaya (astringent),katurasa (pungent), ruksha (dry), laghu (light),sheeta (cold) food, anasana (abstaining from food completely),vishamasana (irregular intake of food),adhyasana (excess intake of food), private cha anne (after digestion), aparane (evening), ativyayama (excess physical activity),prapatana (fall), angabhanga (injury), kshaya (wasting), atishucha (excess cleansing), adhyayana (continuous reading),langhana (fasting),plavana (swimming),jagarana (awake during night),bhashana(excess speech),vegodeerana – dharana (voluntary initiation and suppression of urges), bhaya (fear),shoka(worry),chinta(excess mental activities), etc. lead to vatadoshaprakopa; further resulting in a spectrum of disorders18. The commonest of the etiologies include a history of trauma as twisting of the spine or carrying heavy objects or exposure to cold. Trauma can induce injury to snayu(ligaments), sira(vasculature), kandara(tendon), asthi(bone) and sandhi(joint). In severe cases, it may cause severe intensity to these structures causing sandhi chyuti(dislocation) or asthi bhagna(fracture). The Classical literature mentions different diseases affecting kati pradesha (low back – where most IVD pathologies are manifesting). They mainly present with pain (local or radiating) or stiffness as one of the presenting symptoms in kati pradesha. To be precise, intake of katu rasa results in rookshana, intake of tikta rasa lead to shoshana of dhatus and upadhatus. Kashaya rasa consumption in major proportions leads to karshana. Consuming reduced amount of food cause uttarottara dhatu kshaya, leading to asthi majja kshaya and shosha of upadhatu. Continuous traveling has the potential to produce minor injury or shithilata in dhatu, upadhatu and sandhi leading to various disorders including intervertebral disc disorders.
From the reference of Ashtangahrudaya, sutrasthana; aggravated vayu possess the following characteristic features, they are the following: a) sramsa (drooping down) b) vyasa (dilation) c) vyatha (cutting pain) d) svapa (loss of sensation) e) sada (weakness) f) ruk (continuous pain) g) today (pricking pain) h)bheda (splitting pain) i) sanga (blockage) h) angabhanga (crushing pain) i) sankocha (contraction) j) varta (twisting) k) harshana (tingling) l) tarshana (thirst) m) kampa (tremor) n) parushya (roughness) o) soushirya (cavitation) p) shosha (dryness) q) spandana (pulsations) r) veshtana (covering) s) stambha (stiffness) t) kashyarasata (feeling the astringent taste in this mouth) u) shyavavarna (bluish hue) v) arunavarna (reddish hue)19.
The above-mentioned characteristic features with respect to the vataprakopalakshanas can also be extrapolated with reference to asthi (both vertebra and intervertebral disc – a part of mobile segment) as following: Balabhramsha– Laxity of adjacent structures of mobile segments or laxity of annulus fibrosus,Vartan – Replacement of proteoglycans by collagen fibres, Shosha&Soushirya – Disappearance or degeneration of horizontal and vertical trabeculae, Tarshanam – Intervertebral disc desiccation or dehydration, Angabhanga – Friction of mobile segments, Parushya – Drying or degenerative changes of intervertebral disc due to reduced proteoglycans, Sankocha – Reduced disc spacing or compressed or compromised vasculature, Spandana, Veshtana and Stambhana – Degree of restriction or stiffness, Vyadha, Ruk, Toda and Bheda – Neurogenic or neuropathic pain due to stimulus to various adjacent structures of mobile segments and itself, Svapa – Compromised neural functioning (numbness), Sanga – Impact of neural functioning deficit over other systems including evacuation of bladder, bowel, etc.
Overlooking the embryology from contemporary science and Ayurveda, the intervertebral disc can be designated as asthi. But, considering its location and mechanics, intervertebral disc act as joints that aid in mobility and act as shock absorber. The component predominant in intervertebral disc is shleshakakapha with a predominance of apmahabhoota. With the physiological increase in age or due to the aging process, there will replacement of proteoglycans by collagen or shoshana of kaphadosha takes place due to rookshaguna of vatadosha. The impact of vatadosha due to aging and other traumatic events also cause an impact on the mobile segments itself or to adjacent structures supporting them structurally and functionally.