User:Waeel Ossama Hamouda/sandbox

INCIDENCE:
Overall = 3 and 30%.

Cadaveric dissections 30% > intraoperative surprises > radiological reports 3%.

L5 and S1 (50%) > S2 (30%) > other roots (rare).

Left side > right side Multiple malformations are not uncommon.

EMBRYOLOGICAL ORIGIN:
The embryology of these root anomalies still remains uncertain.
 * 1) Unilateral anomalies of one or more roots, as emergence at a more caudal level, in closely adjacent dural openings or in a common nerve trunk, postulates a defective migration of the roots during embryonic development.
 * 2) Bilateral anomalies of one or more roots, as emergence at a more cranial level, postulates an anomalous emergence of the roots involved from the spinal cord.
 * 3) Abnormal anastomosis between roots may be considered as the result of a link due to a band of nerve fibers or of a complete distal union in a common sheath.

CLINICAL PICTURE:
Conjoined roots usually do not initially produce any symptoms. It is only when further degeneration of discs and/or vertebral joint occurs (often accompanied by stenosing of the spinal canal and of the root canal entrance) that clinically relevant root compressions may be observed.
 * 1) Claudication: (conjoined root > disc herniation) defined as, which can include pain, numbness or weakness but being manifested with activity such as walking or standing and generally relieved with sitting or cessation of activity. In conjoined roots it occurs due to crowding of the conjoined roots in the lateral recess or the intervertebral foramen.
 * 2) Radiculopathy: (disc herniation > conjoined root) defined as symptoms in the leg that correspond to a nerve root distribution, which are present with activity and also with rest. Generally, sitting or standing does not affect radiculopathy.  Conjoined nerve root anomalies may decrease the space available for lumbosacral nerve roots at the lateral recesses, therefore, smaller herniated discs may present with relatively more severe radicular symptoms.
 * 3) Back pain is precedes sciatica and is usually secondary to vertebral bony anomalies which if severe (pedicle & facet) may predispose to spondylolithesis.
 * 4) Neurologic deficits: (disc herniation > conjoined root)
 * 5) Straight leg raising and stretch tests: (disc herniation = conjoined root). However, in conjoined roots significant discrepancy may exists between a progressive sciatica pain and a negative Lasegue’s sign.

MY CLASSIFICATION:

 * I - Intradural anastemosis between any roots
 * II: Extradural anastemosis between any roots
 * III: Abnormal level of origin of any single roots
 * a) cranial origin
 * b) caudal origin
 * c) close dural sleeves for the origin of 2 roots (combination of abnormal cranial and/or caudal origins affecting adjacent roots, i.e. pseudo conjoined)
 * d) common dural sleeve for the origin of 2 roots (one missed dural sleeve, i.e. true conjoined)


 * IV: Extradural intra-spinal division
 * V: Overcrowded foramen:
 * Two complete roots
 * One root with an extradural divison form another root
 * VI: Empty foramen, where adjacent foramen shows:
 * Two roots crowded to pass separately
 * Two roots crowded to pass as an extradural anastemosis

Cannon et al., there are 3 fundamental types of nerve root anomalies:
Type I: (confluent type), in which 2 roots share a common sleeve that originates from the dura mater.

Type II (anastomotic type) in which a normal root bifurcates abnormally after it leaves the dura and branches out to the next caudal nerve.

Type III (transverse type) in which the nerve root leaves the dural sac at almost a right angle.

Postacchini et al. proposed another classification based on 5 different types:
Type I: one or more roots emerge at an abnormal cranial level.

Type II: one root emerges at a more caudal level than normal.

Type III: two or more nerve roots emerge through closely adjacent openings of the dura.

Type IV: two nerve roots emerge from the dural sac in a common nerve trunk.

Type V: an anastomotic branch connects two nerve roots in their extrathecal course.

Kadish and Simmons classified 4 types of anomalies:
Type I: intradural anastomosis between rootlets.

Type II: anomalous origin of nerve root, including: Type III: extradural anastomoses between nerve roots.
 * a) cranial origin
 * b) caudal origin
 * c) combination of cranial and caudal origin affecting more adjacent roots
 * d) conjoined nerve roots.

Type IV: extradural division of the nerve roots.

Neidre classification, there are 3 types of conjoined nerve roots:
Type 1A: the 2 nerve roots arise from a common dural sheath. The cephalad nerve root departs from the conjoined nerve root at an acute angle and passes below its respective pedicle. The caudal nerve root passes caudally within the canal and exit below the sub-adjacent caudal pedicle.

Type 1B: the 2 nerve roots arise from a common dural sheath, the cephalad nerve root departs from the conjoined nerve root at a 90º angle, similar to an exiting cervical nerve root.

Type 2A: (most common) 2 separate nerve roots exit through one foramen, which leave one foramen unoccupied.

Type 2B: (most rare) 2 separate nerve roots exit through one foramen, some nerve rootlets may depart from one of the nerve roots and exit above the pedicle (as an extra additional root; i.e. extradural division of one root) so all foramina have exiting nerve roots and one has two)

Type 3: adjacent nerve roots are connected by a vertically connecting anastomotic segment.

Type 4: any combination of the above.

RADIOLOGY:
MR imaging is a better diagnostic procedure (in comparison to CT) for the differentiation of nerve root anomalies and, in particular, coronal sections furnish a precise definition of the profile of the conjoined/enlarged rootlets.

Signs in axial views:

 * ‘‘Corner’’ sign: asymmetric morphology of the anterolateral corner of the dural sac due to pouching out of the subarachnoid space surrounding anomalous root.
 * "Fat crescent’’ sign: intervening extradural fat between the asymmetric dura (with one root) and the other nerve root.( better seen in T1)
 * “Parallel’’ sign: visualization of the entire parallel course of the nerve root at the disc level.
 * “Bony impressions”: long standing bone remodeling over adjacent bony structures.

Tricks in D.D. :

 * Herniated disc: Conjoined nerve roots are typically located close to the pedicle level in axial slices (above the intervertebral disc space), whereas herniated discs can only be found in this location in cases with migrated disc fragments.The density of nerve roots is almost identical to that of the thecal sacs, and is considerably less dense than that of disc materials.
 * Epidural veins: There is similarity of signal intensity between rootlets and epidural veins. In fact, the internal vertebral veins bind laterally at the level of the disk interspace and medially at the level of the pedicles, where they unite via a connecting vein. However, veins may be distinguished from nerve root anomalies due to the anatomical characteristics of its course and the multiple communications of the internal vertebral veins.
 * Associated bony anomalies: Bony anomalies (congenital aplastic-hypoplastic lumbar pedicle or to lesser extent ipsilateral dysplastic lamina or transverse process) may result from the embryological occurrence of a large retrosomatic cleft. When the cleft is of sufficient size it becomes an absent pedicle. If the pedicular defects are relevant, an absent facet and a retroisthmic defect may be observed.
 * Lateral recess: Conjoined nerve roots and an associated enlargement of the lateral recess may be often confused with a dumbbell tumor or a free fragment of an extruded disk on CT scans.

SURGICAL RISKS:
Intraoperative neural injury, which can be due to:

•Misidentification as a herniated disc after mobilization of the first root.

•Traumatic retraction due to reduced mobility of the nerve.

SURGICAL MANAGEMENT:

 * Asymptomatic and accidentally diagnosed cases do not require treatment. Symptomatic cases (with or without bony alterations), have to be treated in order to relieve neurological signs and symptoms.
 * A wide exposure by hemilaminactomy is necessary to aid in the definition of the conjoined roots and their origin, to allow an adequate visualization and to provide sufficient space for mobilization of the relatively fixed involved roots, thus avoiding the risk of laceration and excessive traction.
 * Creating room for the increased nerves tissue in the exit zone (lateral recess) and foramen is paramount for successful surgery (unroofing of the lateral recess, foraminotomy, partial pediculectomy and medial facetectomy) especially if there are concomitant spinal stenosis & disc herniation.
 * 1) A careful inspection of the disc space is always recommended, because:
 * 2) Due to the busy lateral recesses, missed small herniated fragments may present with relatively more severe radicular symptoms post-operatively. A disc protrusion may be overlooked when the intervertebral space is covered by the anomalous roots.
 * 3) An extruded disc material may be overlooked, if it is hidden in the secondary axilla.
 * When the abnormal configuration and fixation of the roots (clearly depicted by CT and MRI preoperative studies) prevents an adequate exposure of the disc space on the involved side, the removal of the herniated disc through a contralateral laminotomy may be advisable.