INTRODUCTION• Congenital lumbosacral lipomas are the most common form of occult spinal dysraphism.• They are part of a loco-regional malformation involving almost always the skin, the spine and the nervous tissue.• The most characteristic neural anomaly is a low-lying cord.
DEFINITION OF TYPES OFSPINAL LIPOMA (5)• Lipomyelomeningocele • Lipoma of the conus medullaris (most common) • A form of occult spinal dysraphism (OSD) in which a subcutaneous fibrofatty mass traverses the lumbodorsal fascia, causes a spinal laminar defect, displaces the dura, and infiltrates and tethers the spinal cord• Fatty Filum • Lipoma of the terminal filum • The accumulation of fat within the terminal filum and this lesion represents a less severe form of OSD. • The filum is usually thickened in and around the regions of fat deposition.
DEFINITION OF TYPES OFSPINAL LIPOMA• Intradural Spinal Lipoma • Lipoma of the spinal cord. (Rare, 4%, Thoracic) • Fatty accumulations that are completely intradural, have no subcutaneous component, and manifest symptoms when they become large enough to have mass effect. • These lipomas tend to be dorsally situated in the spinal cord and may demonstrate an exophytic component.• Epidural Lipomatosis • Excessive amounts of epidural fat are synthesized. • The most frequent clinical setting for this is in a patient receiving exogenous steroid agents, but it is occasionally seen in cases of severe obesity. • The excessive fat exerts mass effect on the underlying neural structures and can cause a compressive myelopathy or cauda equina syndrome.
DEFINITION OF TYPES OFSPINAL LIPOMA• Spinal Angiolipoma • Benign fatty harmartomas consisting of abnormally differentiated vessels and adipose tissue. • They are commonly found in the skin, muscle, bone, and oral cavity, but there are rare reports of their appearance in the spine or with extension to the brain. • It is recognized that fat accumulations occur for a variety of reasons include as a result of a dysraphic event: • lipomas of the conus medullaris (lipomyelomeningocele) • and lipomas of the terminal filum (fatty filum).
LIPOMA OF THE CONUS(lipomyelomeningocele)• The intradural lipoma is anchored to the conus.• The interface between the two structures is usually resistant and whitish, extending in average from L4 to S3.• The intradural lipoma may compress the cord.• Strictly intradural lipomas are rare.
LIPOMA OF THE CONUS(lipomyelomeningocele)Subtype (3):• Dorsal Variant • Lipoma that arises through a fascial defect and attaches directly to the dorsal aspect of the caudally descended conus medullaris; • All nerve roots emerge from the ventral or lateral surface of the neural tissue and lie in the subarachnoid space. • The lateral nerve roots are sensory, and the more medial nerve roots are motor roots. • Critical to the surgical approach is the junction formed by the lipoma and the spinal cord complex, as well as the position of the dural attachment in relation to that complex.
LIPOMA OF THE CONUS(lipomyelomeningocele)Subtype:• Caudal Variant • Lipoma that exits the area of the terminal filum so that the cord becomes progressively larger caudally. • In this form of lipomyelomeningocele, the nerve roots do transgress the lipoma. • Many of these nerve roots are thought to be non-functional and can be sacrificed after stimulation. • Although this caudal variation is difficult to reform into a tubular structure, the cut end of the lipoma may retract sufficiently cephalad to lessen the likelihood that retethering will occur postoperatively
LIPOMA OF THE CONUS(lipomyelomeningocele)Subtype:• Transitional Form • Has elements of both dorsal and caudal variants. • Viable nerve roots pass through significant amounts of lipoma before exiting. • Typically these are asymmetrical and associated with a rotational component of the spinal cord. • The process of distinguishing among these three types of lipoma is usually straightforward; however, in the literature scant regard is often given to the differences.
Dorsal lipomyelomeningocele:The lipoma is fixed to the dorsal surface of the conusmedullaris. The nerve roots emerge from the spinal cordimmediately anterior to the zone where the lipoma, dura,and conus meet. The associated fatty accumulationpenetrates a bone and fascial defect and is in directcontinuity with a large subcutaneous fat accumulation.Often the filum is thickened and infiltrated by fat.Caudal lipomyelomeningocele:Fat extends from within the central canal of the cordthrough the caudal end where it intermixes with exitingnerve roots. A transverse fibrous band is often present atthe level of the last intact lamina. Release of this band mayresult in dural expansionTransitional lipomyelomeningocele:This lesion demonstrates components of both dorsal andcaudal variants of lipomyelomeningoceles.
Lipoma of the conus (lipomyelomeningocele) Develops both subcutaneously and intradurally The stalk joining these two components passes through a defect of a spina bifida and of the dura Dorsal Caudal Transitional Lipoma of the filum (fatty filum) Involves the whole length of the filum or only part of it. Dural sac is almost constantly normal Roots around are always normal
Lipomas of the filum. Schematic representation of a typical lipoma of the conus MRI, T1operative view sagittal view,of a lipoma showing ininvolving the another case awhole lipoma of the fifilum lum
LIPOMA OF THE CONUS(lipomyelomeningocele)• Recognition, dissection and preservation of the roots and of the interface may be compromised by • (1) the density of the adherences, • (2) a posterolateral insertion of the lipoma on the cord with then intralipomatous roots • (3) an extraspinal extension of the cord
Caudal insertion of the lipoma on the cord.lipoma inserted on theposterolateral aspect of the cord (T1 sequence), the terminal cord ends within the lipoma and the interface is visible.
ASSOCIATED MALFORMATIONS • Most common: cutaneous and vertebral (90% of cases) • Cutaneous stigma on the midline of the back:lumbosacral • Variable diagnostic values; e.g.subcutaneous bump • very high in the case of bump, deviation ofvery suggestive of a the intergluteal fold, or coexistence of two orlipoma more lesions, whatever their type, low in the case of atypical dimple, aplasia cutis, dermal sinus, “queue de faune” • very low in the case of hemangioma, port- wine stain, hypertrichosis, fibroma pendulum, pigmentary noevus, coccygeal dimple minor cutaneous anomaly (deviation of the intergluteal fold)
Lumbar hemangioma (flat or raised, pink or red skinlesion that consists of capillary vessels)Hypertrichosis (localized patch or tuft of hair) Atretic meningocele (skin lesion that looks like a scar and is sometimes called a “cigarette burn”)a Dermal sinus(small hole or opening in theskin that appears as a dimple in the skin) with flathemangioma.b Sacrococcygeal dimple.
ASSOCIATEDMALFORMATIONS• The spina bifida involves often the whole sacrum, extending frequently to L5-4.• Sacral agenesis is rare, but almost constant in patients with urogenital or anorectal anomalies.• Scoliosis is generally related to vertebral bodies malformations or shortening of a leg.• Syringomyelia is noted in 25% of the patients essentially at the lower cord.• Brain anomalies are extremely rare (3%).• Extra-axial malformations are described in almost . of the cases, essentially urogenital and ano-rectal.
DECISION-MAKING:DIAGNOSIS• Prenatal diagnosis • Ultrasonography • from week 17 on the basis of a lumbosacral spina bifida, hyperechogenic skin, low-lying cord and normal intracranial anatomy. • lipoma revealing only at birth or at the very end of the pregnancy
DECISION-MAKING:DIAGNOSIS• Perinatal diagnosis • Cutaneous anomalies • key of the diagnosis. • Congenital deficits • Rare • Resulting from root malformations • Exceptionally obvious, and bilateral • Extremely difficult to assess in neonates and infants • Voiding difficulties • frequently unapparent in the absence of clear incontinence or repeated urinary infections
DECISION-MAKING:DIAGNOSIS• Perinatal diagnosis • Urodynamic studies at birth and every 6 months until the age of two years, and at any age in case of doubt, are recommended. • MRI is the first necessary investigation in the presence of a bump or of deficits to confirm the diagnosis • Sagittal and axial views in T1-T2 weighted images are necessary. • Fat saturation and gadolinium may be useful • Ultrasonography must be proposed first under the age of 2 months in asymptomatic babies with cutaneous anomalies of low or very low diagnostic value • MRI can be avoided if ultrasonography is normal • Brain MRI is unnecessary.
DECISION-MAKING:DIAGNOSIS• Diagnosis in children and adults • Neurological symptoms are predominant • Sphincter disorders, • micturation difficulties, are the most common. • Incontinence results mainly from dysuria, pollakiuria, urgent micturation and incomplete voiding. • Bladder infection or pyelonephritis is not rare, due to urinary retention. • Constipation necessitating digital evacuation is not rare, but frequently concealed by a pseudo diarrhea.
DECISION-MAKING:DIAGNOSIS• Diagnosis in children and adults • Neurological symptoms are predominant • The neuro-orthopedic syndrome • typically unilateral or asymmetrical (clubfoot, equino-varus deformation, clawing of the toes, hypotrophy of the leg) and affects 1/3 of the patients • Sexual dysfunction • almost constant in symptomatic adults. • The caudal syndrome (1.8–5.1%) • associates sacral agenesis, presacral mass and perineal malformation(s). • Only in adulthood when symptoms are limited to moderate bowel dysfunction and unspecific neurological signs
DECISION-MAKING:DIAGNOSIS• Diagnosis in children and adults • Urodynamic studies • should be part of the decision- making work-up, even in the very young and in case of unsuspected urinary troubles. • They may reveal a combination of hyperactive bladder and vesico- sphincter dyssynergia. • Spinal MRI • is necessary in all cases.
DECISION-MAKING:EVOLVING DEFICITS• The diagnosis of evolving deficits is often difficult to make early due to their usually slow progressiveness or even to assess.• Urodynamic studies and/or electromyography of the lower limbs are therefore extremely useful at any doubt.
DECISION-MAKING: FUNCTIONING SCORING SYSTEM• This system takes into account the motor, sensory, vesical and anal handicaps.• Normality is given a score of 5 for motor and urinary functions and of 4 for sensory and anal functions.• Asymptomatic patients have a score of 18.• A normal life is compatible with a score above 15.
DECISION-MAKING: SURGICAL INDICATIONSpresence of congenital deficits presence of acquired or evolving deficits early as possible postoperative evolving deficits mandatory Surgery Redo Surgery
DECISION-MAKING: SURGICAL INDICATIONS Absence of deficits Asymptomatic lipomas of the filum Asymptomatic lipomas of the conus The treatment is not without risk (3.4% of acceptable X neurological complications Pattern of deterioration with or without surgery being at least similar Prophylactic Surgery The pathology is far from being as severe Does surgery have a truly as previously described preventive effect? Patients are better after surgery at first symptom than after routine and early surgeryThe natural history of this malformation remaining unknown
DECISION-MAKING: SURGICAL INDICATIONS Absence of deficitsAsymptomatic lipomas of the filum Asymptomatic lipomas of the conus acceptable X Strict protocol of surveillance Prophylactic Surgery Operated only at first symptom.
DECISION-MAKING: SURGICAL INDICATIONS Absence of deficitsAsymptomatic lipomas of the filum Asymptomatic lipomas of the conus acceptable X Strict protocol of surveillance (1) Thorough and multidisciplinary clinical examinations, at referral, every 6 months until the Prophylactic Surgery age of 2 years, then every year, (2) Urodynamic studies at referral and every six month until the age of the continence (grossly two year of age) and later on at any doubt, (3) MRI at diagnosis, at one year to assure that the lipoma has not increased, and later on every five years until growth is finished.
SURGERY:Principles• Surgery aims to untether the cord, decompress it if necessary, spare the functional nervous tissue and prevent from retethering.• It must be conducted under optic magnification and micro-instruments.• In the case of lipoma of the conus, ultrasonic aspiration and contact laser are extremely useful.• Intra-operative neuro-physiological recording is theoretically useful to distinguish functional roots from fibrotic bands but it did not give the security expected because stimulations were not permanent and recording from sensory roots not totally reliable, in particular from sphincterian rootlets.
SURGERY:Surgery for lipoma of the filum• It is a one-hour procedure.• A small cutaneous incision is sufficient, vertical or horizontal to put a distance between it and the gluteal furrow.• The dural sac is reached through an inter- spinous approach between L5 and S1.• A one-centimeter incision allows recognition, isolation, division and resection of 1cm of filum.• It is frequent that the filum retracts strikingly after its division.
SURGERY:Surgery for lipoma of the conus• The cutaneous incision is vertical on the midline, or horizontal when the lipoma is sacral, to limit risks of postoperative infection.• The resection of the subcutaneous lipoma is, in our opinion, better minimal than total or subtotal to prevent the creation of a dead space in which the CSF could collect postoperatively.• A laminectomy of the lowest or the two lowest normal laminae is, in general, necessary to expose the normal dura and the upper part of the lipoma.• The dural incision is made rostro-caudal, circumscribing the stalk of the lipoma.
SURGERY:Surgery for lipoma of the conus• The division of the subdural adhesions is crucial both to expose the lateral aspects of the lipoma and the underlying roots and to free the cord.• The severity of the adherences, a missing dura replaced by musculo-aponeurotic bundles, or shortness of roots may be such that freeing of the cord is impeded, at least partially.• The degree of removal of the intraspinal lipoma that “total” removal in an attempt to reach the fibrotic interface is doable, but carries the intrinsic risk of injuring the posterior columns, provoking severe and durable pain, trophic ulcers or bladder paralysis.
SURGERY:Surgery for lipoma of the conus• For that reason, we no longer advocate as complete a resection as we did in the past, especially as we have not found any correlation between postoperative results and degree of removal.• Removal of the lipoma must be cautious and necessarily limited in the case of a posterolateral insertion of the lipoma because of the presence of intra-lipomatous roots.• The closure of the placode is not always possible, depending upon its shape and the volume of residual lipoma.• In our experience, the closure edge to edge of the placode does not prevent from postoperative re- adhesion but facilitates an eventual second surgery.
SURGERY:Surgery for lipoma of the conus• The drainage of a terminal syrinx by means of a myelotomy or a drain is not recommended, as we found no correlation between patient’s pre- and postoperative status, and the presence or the size of a syringomyelia.• Many syrinx regress postoperatively.• The enlargement of the dural sac has been recommended to prevent postoperative retethering.• Many prosthetic materials have been proposed, including Gore-Tex more recently, but none has proved to be better than the other.• None prevents from postoperative adherences or reduces the risk of late postoperative deterioration.
SURGERY:Surgery for lipoma of the conus• For these reasons, we ceased to systematically enlarge the dural sac.• In our patients, re-adherences were constant whatever the technique used. Interestingly, of these patients, only a few developed further symptoms related to a tethered cord syndrome, illustrating the fact that fixed cord and tethered cord are different concepts.• The closure of the dura, with or without enlargement, is never waterproof because of constant dural anomalies.• It may also be difficult or impossible when the dura is largely missing, obliging to fix the edges of the dura or of the duroplasty to the paraspinal muscles.• Postoperatively, knowing the frequency of temporary mictional difficulties, we recommend leaving in place a urinary catheter for 2–3 days.
The lipomatous mass is dissected Preoperative view all aroundInterface between the Postoperative viewlipoma and spinal cord
OUTCOME:Long-term postoperative outcome ofsymptomatic patients• It is frequently said that preoperative deficits rarely regress postoperatively.• This is one of the main arguments in favor of preventive surgery.• This is clearly not our experience where only clubfoot, scoliosis and congenital deficits never regressed.• Pain usually totally disappears.• For the rest, the long-term results depend upon the type of lipoma.
OUTCOME:Long-term postoperative outcome ofsymptomatic patients• In lipomas of the filum: • Results are excellent. • 41% of the patients were cured, 12% improved, and 47% stabilized.• In lipomas of the conus: • Results tended to erode with time. • The percentage of patients worse than before surgery increased from 9% at one year to 29% at more than 5 years. • The outcome actually depended upon the immediate postoperative results. (Most of those who clearly improved at one year remained improved.) • Many of those who apparently stabilized or suffered from transient postoperative complications deteriorated with time. • 70% of the patients took advantage of the surgery being either improved or stabilized.
OUTCOME: Long-term outcome of preventive surgery in asymptomatic patients• The outcome differs according to the type of lipoma: • In lipomas of the filum: • Results are as excellent as in symptomatic patients • In lipomas of the conus: • Results erode with time, due to retethering, and underlying myelodysplasia • Patients with minor myelodysplasia and severe retethering have good chances to be improved or even cured surgically • Those with severe myelodysplasia, will probably not improve or even continue to worsen.
OUTCOME: Long-term outcome of conservative treatment in asymptomatic lipomas of the conus• The spontaneous long-term history of asymptomatic lipomas of the conus parallels the long-term outcome after “preventive” surgery.• 30% asymptomatic patients treated conservatively developed symptoms in a 10 year follow-up.
OUTCOME: Re-operations• Re-operations are always difficult and detethering often limited.• There is a consensus in favor of a first redo surgery in the case of spontaneous deterioration following a first surgery.• Further re-operations are more difficult to indicate.• If a first reoperation is usually beneficial, the same cannot be said about further surgeries.
HOW TO AVOID COMPLICATIONS: SURGICAL COMPLICATIONS• In lipoma of the filum: • Surgery is benign in nature and the patient discharged at day 3–5. • The incidence of complication is quasi nil.• In lipoma of the conus surgery (more risky): • Local complications (25%) • The subcutaneous meningocele is the most frequent, often complicated by skin disunion, CSF leak and infection. • Its treatment implies compressive bandages and repeated punctures to apply the skin to the underlying tissues. • Reoperations to close the fistula were necessary in 3% of patients.
HOW TO AVOID COMPLICATIONS: SURGICAL COMPLICATIONS• In lipoma of the conus surgery (more risky): • Transient neurological complications (7.5%) • Urinary and motor deficits were the most common, • They generally cleared up in a few weeks as EMGs and urodynamic studies normalized. • Pain rarely needed aggressive treatment • Permanent neurological complications (3.4%) • Sphincter-related –Urinary retention more common than incontinence • Motor deficits were unilateral, distal and moderate • Trophic ulcers are exceptional, probably consecutive to injury of the interface and the posterior columns.
PREVENTION OF POSTOPERATIVE COMPLICATIONS• To leave the largest possible volume of subcutaneous lipoma in order to prevent the subcutaneous meningocele• To reduce the volume of the residual lipoma later on by lipo-aspiration• To leave a few millimeters of lipoma over the interface in order to not injure the posterior columns• To accept to not achieve a total untethering of the cord as soon as roots are unrecognizable among adherences.
CONCLUSIONS• Lipomas must distinguish lipomas of the fi lum from those of the conus. These two lesions have almost nothing in common from both clinical and therapeutic aspects.• To the simplicity and benignity of the first type, one must oppose the complexity and frequent severity of the second one.• The second conclusion is that treatment of asymptomatic lipomas of the conus is no more acceptable, implying risks and not improving the natural prognosis of the pathology.• “Preventive” surgery in this field remains a dream. The error has been to advocate this concept before knowing the natural history of lipomas and weighting operative advantages.
CONCLUSIONS• In addition to treatment recommendations, we should emphasize the fact that fixed cord does not mean tethered cord.• Following surgery, 100% of the patients develop new adherences tying up again the cord to the dura but, among them, only a few will deteriorate.• The same reasoning should be held when a lipoma is diagnosed in absence of deficits.• The presence of a cord attached to a lipoma and surrounding structures does not mean that the cord is necessarily tethered and at risk of dysfunction.• We should also remind that tethering might not be the only factor causing neurological worsening since some patients aggravate ineluctably whatever has been done surgically.• This certainly suggests that surgery does not ameliorate all of the relevant pathophysiological factors.