Bertolotti Syndrome

Etiology

The etiology of Bertolotti syndrome remains equivocal. There have been numerous reported instances of family members all suffering from lumbosacral transitional vertebrae, suggesting a possible underlying genetic component. The formation of an LSTV is thought to be associated, in part, with mutations in the HOX10/HOX11 genes. HOX genes, also known as homeobox genes, are responsible for the segmentation of the vertebral column into individual levels.[2][4] 

Additionally, the formation of the lumbosacral junction is influenced by biomechanical factors such as how an individual's body weight is transmitted across the SI joints. At this time, Bertolotti syndrome is considered to have a multifactorial etiology that requires further investigation.

Epidemiology

The incidence of Bertolotti syndrome is reportedly between 4 to 8% within the general population.[1][5][6] However, the incidence of an LSTV is far greater, between 4 to 30%.[7][8] 

Due to this discrepancy, many specialists believe Bertolotti syndrome has been vastly underdiagnosed. Despite this variability, the prevalence of an LSTV associated with pain is more than twice as common in males than females.[2][8] 

Additionally, sacralization of L5 has been shown to be more common in males, while lumbarization of the sacrum and the presence of an accessory articulation between L5 and S1 is more common in females.[2][8]

Pathophysiology

Due to the pathological structure and mobility of the lumbosacral junction in patients with Bertolotti syndrome, there are possibly several reasons why pain accompanies an LSTV.

One possible cause of Bertolotti syndrome may arise from an abnormal iliolumbar ligament.[9] In a functionally normal anatomical spine, the iliolumbar ligament is partially responsible for stabilizing the spinal column. However, a recent study suggests that the iliolumbar ligament located on the side of the abnormal articulation in patients with Bertolotti syndrome is far underdeveloped compared to its contralateral counterpart.[10]

Although the transitional articulation may appear to be the most salient source of pain, other associated etiologies that may obfuscate the clinical picture may be discogenic pain and lumbar radiculopathy. There has been an identified association between the presence of an LSTV and disc herniations, as well as facet joint degeneration at the spinal level above the LSTV.[7] 

The disc located directly above the transitional segment, likely L5-S1, has been commonly degenerated at far greater rates than the disc between the transitional vertebra and the sacrum.[7][11] 

Stenosis of the intervertebral foramen has been continuously demonstrated in Bertolotti syndrome, likely due to degenerative changes at the facet joints at the level above the LSTV.[7][12]

History and Physical

A thorough history can help to parse through several possible etiologies of back pain. Patients with Bertolotti syndrome complain of back pain, which may be nonspecific, though other etiologies for pain may confound this. The patient must be specifically probed to determine whether they may be otherwise or adjunctively suffering from concomitant discogenic back pain, facet pain, sacroiliac pain, or radicular pain. 

A full spine exam should be performed in patients suspected of having Bertolotti syndrome to rule out other syndromes such as lumbar spondylosis, degenerative disc disease, lumbar radiculopathy, and neurogenic claudication.  Physical examination may reveal nonspecific tenderness or may also be focally tender to touch. They may also demonstrate a decreased range of motion in the office as well. Provocative maneuvers, reflexes, sensation, and muscle strength should be comprehensively evaluated to rule out other neurological causes of pain.[7]

Evaluation

Imaging is imperative for the accurate diagnosis of Bertolotti syndrome. Plain radiographs of the lumbar spine and pelvis can generally provide ample diagnostic information to show lumbosacral transitional vertebrae.[13] These are quick, relatively inexpensive, minimize radiation, and should be considered first-line imaging modalities. A Ferguson radiograph, which is an AP view of the lumbosacral junction with 30 degrees of cephalad angulation, may be particularly helpful.[14] 

\Review of these radiographs may show enlargement of one or both L5 transverse processes, an apophysis of L5 that articulates with the sacrum, or both. The sacroiliac joints commonly appear normal on plain radiographs.[15]

Advanced imaging in the form of computed tomography (CT) can delineate the lumbosacral junction in greater detail than plain radiographs, especially in patients of greater body habitus, which may obscure the imaging. Osteophyte formation and the extent of fusion at the articulation site can be more carefully scrutinized on CT imaging. Magnetic resonance imaging (MRI) is useful for identifying other lumbar pathologies, including degenerative lumbar intervertebral discs along with disc herniations/annular tears/fissures, as well as areas of sites of neural stenosis.[13] 

Aside from these added benefits of advanced imaging, CT and MRI can also help with vertebral numbering, which may not be apparent on plain radiographs and are critical for treatment planning.

There is no particular laboratory workup that is crucial in the diagnosis of Bertolotti syndrome. However, labs may be considered to rule out other inflammatory or malignant processes. Additionally, if the patient is experiencing any degree of radicular symptoms, an electromyogram (EMG) of the lower extremities may be obtained to help diagnose lumbar radiculopathies versus peripheral neuropathies.

Treatment / Management

Initial management of Bertolotti syndrome should consist of conservative measures. Nonsteroidal anti-inflammatory drugs (NSAIDs) may provide significant relief and are low in cost and generally well tolerated. 

Physical therapy (PT) may also be concomitantly recommended at the time of diagnosis, with treatments aimed to strengthen core musculature, improve spinal mobility, and provide other pain-minimizing modalities. If NSAIDs and PT fail to provide adequate relief, the patient may be recommended for injection therapy.  Directed corticosteroid injections under fluoroscopic guidance into the abnormal articulation are highly effective in providing pain relief and may last temporarily, if not indefinitely.[13][16] (B3)

Injection therapy has the added benefit of not only potentially providing therapeutic effects but can also aid in diagnosing a patient's pain generator and help guide definitive management.

Surgery is reserved for individuals who have failed these aforementioned conservative approaches.  Resection of the enlarged transverse process involved in the LSTV, either unilateral or bilateral, can be an initial surgical option if the pseudo articulation has been determined to be the definitive etiology of pain.[16][17] 

If instability is present at the L5-S1 segment, spinal fusion may be indicated.  While fusion may provide long-lasting relief, this may also hasten adjacent segment degeneration. A decompressive operation may also be indicated if there is a symptomatic central canal or foraminal stenosis present.  The pseudo articulation may facilitate osteophyte formation, which can also potentially be a source of extraforaminal stenosis as well.[16] 

The precise surgical procedure offered to specific patients should be individualized to their symptomatology and unique radiographic findings.

Differential Diagnosis

Patients with Bertolotti syndrome most commonly present with nonspecific low back pain. Unfortunately, the differential diagnosis for low back pain is quite broad, and many can be present simultaneously to cause a multifactorial etiology. Musculoskeletal, neurological, and oncological pathologies should be considered.[14] 

Common causes of back pain include lumbar strains, degenerative disc disease, lumbar disc herniations, annular tears/fissures, lumbar facet arthropathy, facet cysts, Tarlov cysts, scoliosis, and sacroiliac joint pain.[18] 

Meticulous history-taking and physical examination can help to exclude several of these other diagnoses.

When patients experience leg symptoms in addition to lower back pain, providers should also consider compressive lumbar pathologies, including lumbar stenosis/claudication and radiculopathy.[15][18] 

These entities should be taken into consideration along with - and not necessarily exclusive of - Bertolotti syndrome, as lumbar stenosis/radiculopathy, can present as back pain in their own rights due to their own underlying etiologies.  As such, it may be quite common to have tandem reasons for back pain.

Neoplastic processes should also not be overlooked. Lower back pain unrelieved by conservative measures and in the presence of sudden weight loss/gain, intractable night pain, and otherwise unexplained should raise suspicion for a primary or malignant tumor of the lumbar spine/sacrum/pelvis.[19] 

Appropriate imaging and labs will help in the diagnosis of malignancy and, if identified, should be referred for oncologic treatment accordingly.

Prognosis

Bertolotti syndrome can cause chronic back pain in undiagnosed individuals. Conservative management, such as pharmacotherapy, physical therapy, and steroid injections, have been shown to have varying benefits and may provide temporary or potentially definitive relief.[16] 

Those who exhaust these conservative measures and undergo surgical treatment tend to report an improvement in their quality of life but may still have an incomplete resolution of symptoms.[20] 

Ultimately, each patient should be approached independently and have their treatment tailored to their lifestyle and needs.

Complications

The LSTV of Bertolotti syndrome are niduses for abnormal mobility and mechanics of the spine. Consequently, greater stress is typically dispersed onto the adjacent segments of motion. These increased forces that the adjacent segment experiences are at risk for accelerated disc and facet joint degeneration, arthrosis, and ultimately neural stenosis.[7] 

The surgical treatments for Bertolotti syndrome carry their inherent risks. As with all surgical procedures, there is a risk of bleeding at the surgical site, infection, and the need for the patient to have future operations if the first was unsuccessful. These procedures also risk nerve injury due to the surgery’s proximity to the nerve root canal and the spinal cord.[17][21] 

Although surgical complications are rare, it is imperative to discuss these with the patient.