Anthony Dacunha, MD
Volume 03, Issue 04, July 2001
PART 1 -THE LUMBAR SPINE
1- DEFINITION: Radiculopathies are conditions which affect the exiting spinal
nerves. Pain with specific characteristics is the main symptom. A dysesthesic pain
radiating from the spine to certain areas of the limbs and chest help localize the
root/roots involved. Cauda Equina Syndrome is the name of a condition in which
multiple roots are affected. Spinal canal stenosis, large central herniated discs and
intrathecal tumors cause the Cauda Equina Syndrome.
2- ANATOMY: There are 8 cervical roots, 12 thoracic roots, 5 lumbar roots, 5
sacral roots and 1 coccigeal root in each side. In the lumbar area the L5 and SI
roots are the most important in everyday clinical practice. In the neck it is
important to know that only 7 vertebrae are present for the 8 roots. In the cervical
spine the root is named by the vertebral body below. At the junction with the
thoracic spine, above the 7th cervical vertebra the root is C7 and below is C8.
From Tl the roots are named for the vertebral body above. The sensory ganglia are
located distally to the roots. This is very important for the clinician and the
neurodiagnostic consultant, considering that radiculopathies show normal findings
in the sensory NCS as opposed to the plexopathies which are conditions involving
the nerves distal to the sensory ganglia. The spinal cord ends at the Ll level but a
few patients may have the spinal cord tethered at lower levels by lipomas from
3- CLINICAL CONSIDERATIONS: The working diagnosis of a radiculopathy is
given by the history. Do not expect findings in the neurological examination in the
majority of patients. The explanation for this is in the complex neuronetwork found
at the lumbosacral and brachial plexus. A detailed history is decisive and can give
the location of the root affected. For instance, the SI root pain stops at the calf-
ankle and the little toe feels numb and tingly. The L5 root pain settles at the
popliteal fossa and the big toe feels numb and tingly. The lack of sensation in the
perineal region is typical of the Cauda Equina Syndrome. The absence of the ankle
reflex is common in the SI radiculopathies. Difficulties in tapping the foot on the
floor and doing a deep knee bend are seen also in SI radiculopathies. The straight
leg raising test is valuable, but only if done correctly. Pain alone is not enough to
call the SLR test positive. It has to happen at around 45 degrees and reproduce the
radicular pain as described in the history. The presence of tripping and crossing of
symptoms to the other leg is clinically significant.
4- NEUROIMAGING: The development of the MRI in the late 1980's was a
decisive step in the diagnosis and understanding of the radiculopathies. The plain
X-Rays, the myelogram with pantopaque and the CT-myelogram were used but
they are not nearly as valuable as the MRI. For the past five years the constantly
evolving technology of the MRI reached the point in which a good MRI is more
than enough for the imaging part of the evaluation of a radiculopathy. The CT-
myelogram has a small niche, and this is in the evaluation of root avulsion from the
cervical spinal cord. The MRI with contrast is valuable for the evaluation of
patients with a history of previous surgery for herniated discs and helps distinguish
scar tissue from a recurrent herniated disc. Discograms are useless and dangerous.
5- ELECTRODIAGNOSIS: Another major development in the evaluation of the
radiculopathies is the use of Nerve Conduction Studies, Needle Electromyography,
Somatosensory Evoked Potentials and the Motor Evoked Potentials (Magnetic
Stimulation). In the 1980's the computer made the electrodiagnosis instruments
more easy to use and reliable. Today the evaluation of a radiculopathy without
electrodiagnosis is incomplete. The EDX can be invaluable for the surgeon prior to
a decision to operate. A patient with a radiculopathy and a peripheral neuropathy
("Double crush syndrome") will have very poor results from the surgery. A patient
with a herniated disc at L5-SI but with electrodiagnostic evidence for a L5 root
lesion may not benefit from the surgery considering the small chance of the L5
root to be affected solely by a L5-SI herniated disc. The EDX may also give
information about reinnervation and chronicity. A SI root which is permanently
damaged shows large MUAP's with no sign of reinnervation or muscle membrane
instability; and this indicates an almost certain poor result if the surgery is done.
NCS: The nerve conduction studies for the lumbar radiculopathies are invaluable
mainly if a SI root lesion is suspected. The H-reflex is the most important test and
should be done in every case of lumbar radiculopathy. The H-reflex is the EDX
equivalent of the ankle reflex. The test is done by stimulation of the tibial nerve at
the popliteal fossa and recording in the soleus muscle. The reflex may be absent in
patients over 60 years of age. The most important information is from a unilateral
prolongation of the latency indicating a SI root lesion. In the advanced
radiculopathies the amplitude of the CMAP's may be reduced. The F-waves are not
helpful in radiculopathies.
Needle EMG: This is the best test and should be done with a plan. First the distal
muscles are tested. If the Tibialis anterior shows evidence for "denervation" a L5
root lesion is suspected; then the Tensor Fascia Lata should be tested which is a
proximal muscle by a different nerve. Last the paraspinals are tested. The
paraspinal muscles are invaluable to the EDX consultant but the yield is low. If the
gastrocnemius muscle shows evidence of "denervation" then a Sl root lesion is
suspected and the Gluteus Maximus muscle should be tested, plus the paraspinals.
SSEP's (Somatosensory Evoked Potentials): Are indicated when a Cauda
Equina Syndrome is suspected (spinal stenosis, large central herniated discs and
intrathecal tumors). The localization of the root involved is invaluable for the pain
management physician to guide the selective nerve root blocking procedure. The
identification of a peripheral neuropathy is important for the decision to start any
type of treatment for an isolated radiculopathy.
6- TREATMENT: Most radiculopathies resolve with or without treatment. A few
chronic cases, if a single root is identified by the EDX, may benefit from selective
root blocking procedures. Acute or subacute large herniated discs compressing the
root in the lateral recess, with no evidence of chronicity in the EDX, give the best
results from surgical intervention (laminectomy in the lumbar area). Cauda Equina
Syndrome from large central herniated discs should be corrected surgically. Rare
cases of radiculopathy are caused by multiple myeloma, synovial cysts arising
from the facets, compression by osteophytes, neurinomas and other neoplasias.
Spinal Canal Stenosis is with an ill reputation as far as surgical procedures are
concerned and is responsible for the vast majority of the so-called " failed back
syndromes" (See Addendum).
Anthony Dacunha, MD, Editor
Board Certified in Neurology
NEWSLETTER - ADDENDUM
THE "FORGOTTEN RADICULOPATHIES"
The upper lumbar root/nerve lesions are frequently overlooked by clinicians and
the lumbar canal spinal stenosis has a poor previous record. Both are considered
the "forgoffen radiculopathies".
1- THE UPPER LUMBAR ROOTS: The LI, L2 and L3 roots are frequently
forgotten by most non-neurologists but it is important to know a few facts related
to these nerves.
The genitofemoral nerve, the ilioinguinal nerve and the lateral femoral cutaneous
nerve are all originated at the LI -L2-L3 group of roots and are exclusively
As opposed to the lower roots, in the majority of the cases, one of the nerves above
is involved and not the root itself. The genitofemoral nerve supplies sensory
innervation to the groin and inner aspect of the thigh. The ilioinguinal nerve
supplies sensory innervation to the pubic area and genital area (not to the
perineum, which is innervated by the pudendal nerve). The two nerves above are
frequently injured during surgical procedures in the lower abdomen, mainly
gynecological laparoscopies. The genitofemoral nerve and the ilioinguinal nerve
are superficial in the anterior wall of the lower abdomen and they cross each other
at about the place where appendectomies are made. The lateral femoral cutaneous
nerve entrapment at the inguinal ligament is the cause of Meralgia Paresthetica,
which was the subject of an EDX Newslefter in August of 2000. Rarely a herniated
disc; at LI-L2 or L2-L3 may cause the symptoms in the area of the three nerves.
The iliohypogastric nerve is not important from a clinical point of view and runs in
the retroperitoneal region and may be affected by neoplastic processes. Only the
lateral femoral cutaneous nerve has EDX available for its evaluation.
2- SPINAL CANAL STENOSIS: The diagnosis of spinal canal stenosis is today
a source of embarrassment for many in the medical profession, much like Reflex
Sympathetic Dystrophy (RSD). After neuroimaging became available, mainly in
the 1980's, a legion
of patients was submitted to multilevel laminectomies with the placement of metal
plates and many pedicle screws for the treatment of lumbar spinal canal stenosis.
Many patients had up to five operations in their lower back and ended up labeled
"failed back syndrome". Many patients were involved in car accidents after the
operations and the plates and screws broken and scattered all over the lumbar
region. As a result, today, few doctors talk about spinal stenosis, and the
radiologists avoid even mentioning the "dirty" word. As a matter of fact Lumbar
Spinal Canal Stenosis is a common condition.
The typical patient starts with recurrent lower back pain at an early age. They start
to complain of lower back pain in the their 20's or 30's, and frequently there is a
family history of lower back pain or even a " failed back syndrome". Later on
sciatic pain starts and evolves to become bilateral with the typical forward bending
posture and severe pain with extension of the lumbar spine. The reports from
MRI's are usually not helpful since the radiologists frequently avoid the dreadful
diagnosis. The patients with lumbar spinal canal stenosis are not candidates for
surgical procedures and do not benefit, in general, from selective nerve blocking .
The patients with spinal canal stenosis are usually the ones which are drug seeking
and rejected by most doctors, even the pain management specialists. The use of a
static bike and water aerobics is recommended for this population of sufferers.