Below are terms and definitions used in the LOBAK mobile app and website to help explain and clarify some relevant medical terminology. If you have any further questions, please visit the FAQ or Contact pages.

Anesthesia, General – being “put to sleep”.  For spine surgery patient is put to sleep on their back, then turned onto the stomach, after intubation (an endotracheal tube is inserted through the mouth).

Anesthesia, local – area of surgery numbed by a local anesthetic injection while patient has intravenous sedation.

Annulus Fibrosus – see Disc

Babinski Sign (extensor plantar reflex) – see section “Brain and Spinal Cord”.

Bent-Leg Raising Test – used as a check for true sciatic pain on straight-leg raising; flexing the knee while raising the leg takes the stretch off the sciatic nerve.

Cauda Equina – the spinal nerves within the spinal canal that have exited the spinal cord but must pass through the lumbar spinal canal to find their segmental exit.  It is said to look like a horse’s tail (Latin: cauda, tail; equina, horse).

Clonus, Ankle – see section “Brain and Spinal Cord’.

Corkscrew Motion of Spine – a sciatic scoliosis that can occur on forward bending, usually seen with disc protrusions causing leg pain.

Crossed Straight-Leg Raising Test – increased pain in a painful leg when raising the opposite (non-painful) leg.  Diagnostic of a lumbar herniated disc.

Dermatome – an area or strip on the skin supplied primarily by a single spinal nerve root. There is overlap but also some autonomous zones.  In the lumbar spine, the L4 root autonomous zone covers an area below the knee, the L5 root the big toe, and the S1 root the little toe.

Disc, Disk, Intervertebral Disc, Spinal Disc – a cartilage pad between the vertebrae like a “jelly donut”, with damp crabmeat-like cartilage in the center (the nucleus pulposus) and a tough, fibrous ligament ring holding it in by connecting two adjacent vertebrae (the annulus fibrosus)

Disc, Bulging – a normal aging process due to decrease water content of the nucleus pulposes, allowing the disc to compress and bulging the annulus diffusely.

Disc, Degenerated – narrowing of the disc space due to thinning of the nucleus and     arthritic bone formation at the edges of the annulus.

Disc, Extruded – seen on imaging as disc material focally protruding with a small waist at the annulus, indicating that the nucleus pulposus has torn through the annulus but is probably still connected to the nucleus pulposus.

Disc, Herniated – some of the annulus fibrosus has stretched or torn and the nucleus pulposus has protruded outside the edges of the adjacent vertebrae.  These can also be sub-classified as focal protrusions, extrusions, or sequestered disc fragments.

Disc, Protruded – disc material seen outside the edges of its surrounding vertebrae on an imaging study.  If the protrusion is diffuse it is the same as a bulge in which case it is considered normal by most spine physicians (a radiologist calls everything he sees).  A Focal protrusion of a part of the disc annulus is considered abnormal and can also be called a herniation of the disc.

Disc, Sequestered, Sequestration of – a soft tissue mass seen on imaging, assumed to be nucleus pulposus material, that is not contiguous with the disc annulus and may have migrated within the spinal canal.

Disc, Slipped – a layman’s term not used medically.  The entire disc does not slip in and out.

Epidural Steroid Injections – I have only found these as a temporary help, but giving steroids by mouth (the Medrol Doseopak is popular) can aksi give quick temporary relief.  An ESI should be done under X-ray fluoroscopic control. It requires a “not quite” spinal tap, stopping the needle just before it gets to the spinal fluid, and injecting a long-acting steroid inside the spinal canal but outside (epi) the dural sac containing spinal nerves and fluid.  A randomized, double-blind study years ago was published in the prestigious New England Journal of Medicine showing that ESIs were no good in treating HNP.  Two groups of similar patients with lumbar HNPs were given injections, one with steroids and the other with saline placebo; more in the group getting steroids eventually needed surgery.  The spinal canal is a region of low resistance to infection. Injecting substances into that area risks infection that can lead to a paralyzing abscess, meningitis and even death.

Extensor Hallucis Longus (big toe extensor) muscle – cocks up the big toe; supplied by the L5 nerve root.

Foot Drop – the inability to cock up the foot at all.  Usually caused by a severe impingement of the L5 root by a HNP.  Considered a surgical emergency if recovery is to be possible.

Gastrocnemius (calf muscle) – strong muscle; can allow heel to sag on toe-walking if very weak. Supplied by the S1 nerve root.

MIS – minimally invasive surgery

MISLD, Micro-operative Intersegmental Lumbar Decompression – MIS for lumbar spinal stenosis.  If a fusion is needed, can be done MIS using Aspen clamp.  Requires general anesthesia. See Treatment, Surgery section.

MLD, Microlumbar Diskectomy – MIS day surgery for  HNP using an operative microscope and a 2 cm incision.  In obese people, the incision often must be 2-3 inches long.  Requires an endotracheal tube for general anesthesia because, with person on stomach asleep, airway must be kept open.  For details, see refs. (6,9,38). See Treatment, Surgery section.

Muscle Spasm – tightness of muscles in the lower back, possibly causing a “flat back”; less often even causes a sideway curvature (scoliosis).  Is involuntary, probably as a way reduce painful motion of the spine.

Nerve, Femoral – powers the quad muscle, which raises the foot off the floor when     sitting.  It is supplied mostly from the L3 nerve root, which exits the spine between L3 and L4 vertebrae and is not connected to the sciatic nerve.

Nerves, Mixed – nerves that carry both motor power to muscles and sensation back     to the brain

Nerve, Peroneal – a branch of the sciatic nerve that wraps around the outside of the knee and supplies muscles that cock up the foot.  It carries nerve fibers from the L5 nerve root, which comes off the spine between the L5 and S1 vertebrae.

Nerve, Posterior Tibial – a branch of the sciatic nerve that helps lift the heel and also twists the ankle inward.  It carries nerve fibers from the S1 nerve root, which exits the spine through the first sacral foramen (between the normally fused first and second sacral vertebral segments)

Nerve Root – that portion of a spinal nerve that is penetrating the dural sac to exit the bony spinal canal.  It carries some dura and surrounding spinal fluid around it for a short distance and is moveable.

Nerve, Sciatic – a large nerve outside the spinal column made up of connections of several spinal nerves after they exit.  It contains nerves from lumbar and sacral segments of the spinal cord.

Nerves, Spinal, – that part of the nerves that are still within the spinal canal

Nucleus Pulposus – see Disc

Scoliosis – a sideways curve in the spine.  When brought on by pain, is called a “sciatic scoliosis” and is not due to bony deformity.

Spinal Cord – solid structure in the spinal canal that carries signals from and to the brain by giving off mixed nerves in segments. The spinal cord ends about where the last rib comes off.   There is no spinal cord in the lumbar spine.

Straight-Leg Raising Test – increased leg pain on raising a painful leg without bending the knee.  It stretches the sciatic nerve and indicates a disc protrusion impinging one of its nerve roots.

Synovial Cyst – a rounded soft tissue mass attached to a facet joint.  Facet joints have a synovial membrane that can protrude enough to sometimes cause irritation of a spinal nerve exiting close by.

Tibialis Anterior – a strong muscle that cocks up the entire foot; can allow the foot to drop some during heel-walking.