How do you recognise radicular, dry and cluster pain?

Lumbosacral nerve root from the spinal canal into the sacral plexus, and the collection of the sciatic nerve trunk, so when any of the three are involved, it can cause some similar symptoms and signs. Mainly manifested in waist and leg pain, numbness, movement and reflex dysfunction and a positive straight leg raising test, etc., some of the features are often difficult for beginners to recognise, leading to misdiagnosis. In fact, the pathoanatomical locations and characteristics of the three lesions are not consistent. With the exception of rare cases where two or three may occur simultaneously, these characteristics are typically singular and distinct.

Radicular pain is most commonly associated with lumbar disc herniation, lumbar spinal stenosis (including lateral fossa stenosis), and lumbar spinal tumours.

(1) Paravertebral pain: The main features of radicular pain are paravertebral pain and radiation to the lower limbs due to the simultaneous involvement of the dorsal and lateral branches of the spinal nerve roots of the affected segment. Dry pain and cluster pain do not typically present with radicular pain.

(2) Limitation of lumbar spine movement: Lumbar spinal stenosis mainly limits back extension, while lumbar disc issues may limit lumbar back extension, forward flexion, and affected side flexion. Intradural tumours may also cause varying degrees of lumbar spine movement limitation at different stages of the disease. However, dry pain and plexiform pain do not exhibit this feature.

(3) Cervical flexion test: Zhao Dinglin et al. conducted a cervical flexion test on 200 patients with radicular pain, and the positive rate was over 95%. This is because the cervical spine is in a state of forward flexion, which increases tension and pressure on the affected nerve roots through the dural sac and root cuff, exacerbating the pain. The study found no evidence of dry pain or plexiform pain.

(4) Symptoms of spinal nerve root localisation: The sensation, movement, and reflexes of spinal nerve roots have clear localisation characteristics depending on the spinal ganglia. For instance, the dorsal skin sensation of the first and second toes of the foot is mainly innervated by the lumbar nerve root, while the lateral edge of the foot and the little toe are innervated by the sacral 1 nerve root. Radicular pain, sensory disorder, and reflexes are more involved than the range of dry pain and cluster pain.

In the past, clinical diagnoses of dry pain were commonly referred to as 'sciatica' or 'sciatic neuritis'. However, recent scholarship suggests that lesions of the pelvic outlet of the sciatic nerve, such as tumours, adhesions, pudendal muscle compression, and inflammatory stimulation, are the primary causes of dry pain. The main features of dry pain are not affected by subjective evaluations and are characterised by a lack of moisture.

(1) Pressure points: These are mostly located in the pelvic outlet, specifically around the ring jump point. Radioactive lower limb pain occurs when local deep pressure is applied, and its range is obviously larger than radicular pain. About 60% of the diseased side is accompanied by rouge point (tibial nerve course) and peroneal point (common peroneal nerve course) pressure and radicular pain. There is no obvious pressure and percussion pain in the lower lumbar region.

(2) Lower limb rotation test: The test for internal rotation is positive if it is solely caused by outlet adhesion. If the pudendal muscle is also involved, external rotation is also positive.

The symptoms of dry localisation are manifested as sensory, motor, and reflex deficits in the tibial nerve and peroneal nerve innervation area. The range of involvement is wider and limited to the spinal nerve roots within the range of lumbar 4 to sacral 2.

(4) Plantar numbness: Root sensory disorders often do not involve the entire plantar area. However, according to Zhao Dinglin and other statistics, more than 90% of dry pain cases exhibit plantar numbness.

 Plexus pain :can be caused by tumours, chronic inflammation, and adnexal diseases in the pelvis, which can affect the sacral plexus and result in symptoms. The most common nerves affected are the sciatic nerve trunk, femoral nerve trunk, and superior gluteal nerve.

(1) Multi-stem pain: In the same case, sciatica, thigh, sacral and knee pain may be present. These symptoms can occur simultaneously or alternately, depending on the severity of the lesions. There may be differences in the degree of involvement between several nerve trunks.

(2) Lumbosacral percussion test: The difference between this test and radicular pain is that when percussion is applied to the lumbosacral region, the patient not only experiences no pain but also feels comfortable. In contrast, pelvic space-occupying lesions cause pain, often severe.

(3) Pelvic examination: Pelvic pain is more common in female patients; therefore, a gynecological examination is necessary to exclude gynecological diseases before making a diagnosis. Additionally, to exclude tumours, pelvic palpation and, if necessary, anal examination should be performed. Orthopantomograms and oblique films of the pelvis should be taken after a cleansing enema. Barium enema or cystography can be used for those suspected of having intestinal or urinary tract tumours.

(4) Reflex changes: The knee reflex and Achilles tendon reflex may be weakened or disappear simultaneously.