Anatomical gates for pain relief due to cervical and lumbar disc disease

A middle aged lady, 48, with no co-morbidities, had severe chronic neck pain, right sided radiculopathic pain of VAS score 9, and occasional episodes of severe vertigo, for the last 15 years. She had normal neurological examination of both her upper limbs. MRI showed C5/C6 prolapsed disc. Patient had had Gate A injection in her right axilla. 3 mL of 2% lignocaine was added to 7 mL of distilled water in a 10 mL syringe. Patient was in supine position with head turned to other side, and 90 degrees abduction and full external rotation of shoulder with 90 degrees elbow flexion. The axillary artery was palpated and the needle advanced above the artery into the bicipital groove of the humerus. After touching the groove, the needle was retracted only enough to inject the lignocaine.
The patient has been pain free after the injection for eleven months now.
A 62 years old man with hypertension only, described severe right upper limb radiculopathic pain, VAS score was 9 for the last 4 weeks for which oral medications did not help. He had normal neurological examination in his upper limbs and MRI confirmed prolapse of C5/C6 disc. He was given Gate B injection, in the carpal tunnel injection with lignocaine only. The patient described 75 % pain relief 30 min after the injection and complete relief of pain one week after the injection for the last eight months.
An old lady, 66 y, with known chronic lower back pain and left sciatica, VAS score 7 for more than ten years. She had normal neurologic tests and SLR. MRI showed L4/L5 prolapsed disc. She was given Gate C injection one year back. The injection was made in the tarsal tunnel. 10 mL syringe, 23G needle (7 mL total volume - 3 mL 2% lignocaine plus 4 mL distilled water). It takes around 30 min for pain relief to be sensed. Patient positioned supine with external rotation of hip in the same side of injection. The needle was introduced through a point just distal and posterior to medial malleolus. The needle was in 45 degrees inclination to horizontal plane with the needle tip towards the patient head and facing posteriorly progressing from distal to proximal with needle going parallel to tibia shaft. The injection volume was deposited at different depths as the needle was progressed deeper with aspiration before each injection in order not to miss the tarsal tunnel. The patient felt paresthesia in her heel in 10 min after the injection was made into the tarsal tunnel. and has been complete pain free till now.
A young man of 24 years of age presented with severe right sided sciatica for six months. Patient had normal neurology in both lower limbs and his SLR was 60 degrees. MRI showed L5/S1 prolapsed disc. He had an ESI that failed to relieve his pain. This patient was given Gate D injection and is pain free for the last two months following the injection
Gate D is an injection in the upper tibiofibular joint with 10 mL syringe (3 mL of 2% lignocaine plus 7 mL of distilled water). Gates A and D injections caused no motor or sensory deficits in the upper and lower limbs respectively.
How come a peripheral injection can relieve pain when the cause of pain lies more proximally? How can the effect of a simple lignocaine injection last for months when the half-life of lignocaine is only about one hour? To understand it we have to understand the following: After nerve injury hyperexcitability and spontaneous firing develop at the site of injury and also in the dorsal root ganglion cell bodies. This hyperexcitability results at least partly from accumulation of sodium channels at the site of injury.5 Pain is related to excited nerves and disturbance in voltage-gated sodium channels. The relationship between voltagegated sodium channels and pain has been reported in many published studies.6-11 Simply by giving lignocaine, which is a sodium channel blocker, you are resetting the electrogenicity of nerves like resetting a jammed laptop. The local anesthetic molecule consists of three components: (a) lipophilic aromatic ring, (b) intermediate ester or amide chain, and © a terminal amine.1 The aromatic ring improves lipid solubility.1–3 The nerve membrane consists of a double lipid layer and a protein layer and therefore, the property of enhancing lipid solubility contributes to increased potency of the anesthetic agent as more of the available drug can diffuse through the membrane.12 Myelin sheath is characterized by a high proportion of lipid (70 to 85%).13 Lignocaine will diffuse through the myelin sheath covering the nerve and in case of blocking a peripheral nerve the diffusion will carry on throughout the whole nerve blocking the sodium channels, which are accumulated at the site of injury. The hypothesis is diffusion will occur through the uninterrupted myelin sheath covering the main nerve and its branches and by injecting one division of the main nerve the lipid based chemical will diffuse to the main nerve and its other branches.
The authors hope that these new injections are scrutinized further in big studies to prove their efficacy. The author theorizes that the diffusion of a particular chemical through the myelin sheath of nerves and its efficacy in treating pain depends on the following criteria: 1) The Lipid solubility of the injected chemical. The more the solubility the more diffusion through the myelin sheath (which is mainly made off lipid), the more solubility the better. 2) The volume of the injected chemical. The more volume the more is the effect. 3) Distance from the Dorsal Root Ganglia. The shorter the distance the better the effect. 4) Characteristics of the myelin sheath of different nerves, as the different nerves differ in the content of myelin. 5) The distance of the injection to the nerve. The shorter, the better is the effect. Of course the above-mentioned points need extensive research studies to prove or refute them and the author suggests the use of contrast material, as it is used in myelography, to prove that the chemicals can diffuse and travel proximally in the peripheral nerves. Contrast material, for example, can be injected in the tarsal tunnel and followed up by radiology done at various times to study this phenomenon. With this approach, we could gain a lot of knowledge in regards to nerve function and the scope of that knowledge would be limitless.
With the discovery of the voltage-gated sodium channel blocker gates, it has become easy to diagnose and treat many conditions in the musculoskeletal systems, which have been treated with difficulty and poor results. These gates injections are an easy, safe and effective method of pain management related to nerves in the upper and lower limbs.