While this test is positive in about 90% of people with sciatica, approximately 75% of people with a positive test do not have sciatica. Straight leg raising of the leg unaffected by sciatica may produce sciatica in the leg on the affected side; this is known as the Fajersztajn sign. The presence of the Fajersztajn sign is a more specific finding for a herniated disc than Lasègues sign. Maneuvers that increase intraspinal pressure, such as coughing, flexion of the neck, and bilateral compression of the jugular veins, may transiently worsen sciatica pain. Medical imaging
Imaging modalities such as computerised tomography or magnetic resonance imaging can help with the diagnosis of lumbar disc herniation. The utility of MR neurography in the diagnosis of piriformis syndrome is controversial.Discography could be considered to determine a specific discs role in an individuals pain. Discography involves the insertion of a needle into a disc to determine the pressure of disc space. Radiocontrast is then injected into the disc space to assess for visual changes that may indicate an anatomic abnormality of the disc. The reproduction of an individuals pain during discography is also diagnostic. Differential diagnosis
Cancer should be suspected if there is previous history of it, unexplained weight loss, or unremitting pain. Spinal epidural abscess is more common among those who have diabetes mellitus or immunodeficiency, or who have had spinal surgery, injection or catheter; it typically causes fever, leukocytosis and increased erythrocyte sedimentation rate. If cancer or spinal epidural abscess is suspected, urgent magnetic resonance imaging is recommended for confirmation.
Pathophysiology
In terms of the mechanism of congenital hyperinsulinism one sees that channel trafficking requires KATP channels need the shielding of ER retention signal.E282K prevents the KATP channel surface expression, the C-terminus (SUR1 subunit) is needed in KATP channel mechanism.R1215Q mutations (ABCC8 gene) affect ADP gating which in turn inhibits KATP channel. Diagnostic
In terms of the investigation of congenital hyperinsulinism, valuable diagnostic information is obtained from a blood sample drawn during hypoglycemia,  detectable amounts of insulin during hypoglycemia are abnormal and indicate that hyperinsulinism is likely to be the cause. Inappropriately low levels of free fatty acids and ketones provide additional evidence of insulin excess. An additional piece of evidence indicating hyperinsulinism is a usually high requirement for intravenous glucose to maintain adequate glucose levels, the minimum glucose required to maintain a plasma glucose above 70 mg/dl. A GIR above 8 mg/kg/minute in infancy suggests hyperinsulinism. A third form of evidence suggesting hyperinsulinism is a rise of the glucose level after injection of glucagon at the time of the low glucose.Diagnostic efforts then shift to determining the type- elevated ammonia levels or abnormal organic acids can indicate specific, rare types. Intrauterine growth retardation and other perinatal problems raise the possibility of transience, while large birthweight suggests one of the more persistent conditions. Genetic screening is now available within a useful time frame for some of the specific conditions. It is worthwhile to identify the minority of severe cases with focal forms of hyperinsulinism because these can be completely cured by partial pancreatectomy.