Surgical evaluation and management of lumbar synovial cysts: the Mayo Clinic experience

Juxtafacet cyst infection

PURPOSE

In the realm of spinal surgery, infections have multiple etiologies and sites of origin. In this case series, we describe a juxtafacet cyst spinal infection that can often be missed or attributed to common symptomology of benign processes despite florid infection.

METHODS

In rare instances, the juxtafacet cyst may become infected and require direct intervention. This case report attempts to describe the prodrome leading to such a diagnosis and two different ways to manage an infected facet cyst.

RESULTS

Management of spinal infections varies due to the multiplicity of causes and location of infections. The juxtafacet cyst infection should remain a part of the differential diagnosis for low back pain as their presentation often mimics more common presenting complaints.

CONCLUSIONS

In our two patient presentations, both were diabetics and had remote histories of cancer that necessitated chemotherapy or radiation therapy. They also seemingly had de novo onset of infected juxtafacet cyst. The variety of causes and presentations of spinal infections should heighten the astute surgeon to be suspicious of these entities and thus intervene early with appropriate management.

Microsurgical excision without fusion as a safe option for resection of synovial cyst of the lumbar spine: long-term follow-up in mono-institutional experience

Spinal synovial cysts are cystic dilatations of the synovial membrane that may arise at all levels of the spine. We describe our experience, paying attention to diagnosis, surgical treatment, and long-term follow-up. Between 1995 and 2007, 18 patients were surgically treated. Of these, three patients were excluded from the study because they presented spinal instability at pre-operative assessment. All patients were evaluated pre-operatively with CT, MRI, and dynamic X-rays, and underwent surgery for removal of the cyst by hemilaminectomy and partial arthrectomy. All patients were evaluated with early MRI and had a minimum 2-year follow-up by dynamic X-rays. None of the patients required instrumented fusion due to the absence of radiological signs of instability on the pre-operative dynamic tests. In all patients, there was an immediate resolution of the symptoms, with evidence of complete removal of the cysts on post-operative MRI. At 2-year follow-up, all patients underwent dynamic X-rays and responded to a questionnaire for evaluation of outcome. None of them showed signs of relapse. The gold standard for treatment is surgery, even though other conservative treatment regimens have been proposed. Correct surgical strategy relies on pre-operative assessment of biomechanical stability for deciding whether patients need instrumented fusion during cyst removal. Patients with no instability signs are suitable for hemilaminectomy with partial arthrectomy, preserving 2/3 of the medial portion of the articular facet, because this represents a valid option of treatment with a low risk of complications and a low rate of relapse.

Recurrent back and leg pain and cyst reformation after surgical resection of spinal synovial cysts: systematic review of reported postoperative outcomes

BACKGROUND CONTEXT

With improvements in neurological imaging, there are increasing reports of symptomatic spinal synovial cysts. Surgical excision has been recognized as the definitive treatment for symptomatic juxtafacet cysts. However, the role for concomitant fusion and the incidence of recurrent back pain and recurrent cyst formation after surgery remain unclear.

PURPOSE

To determine the cumulative incidence of postoperative symptomatic relief, recurrent back and leg pain after cyst resection and decompression, and synovial cyst recurrence.

STUDY DESIGN

Systematic review of the literature.

PATIENT SAMPLE

All published studies to date reporting outcomes of synovial cyst excision with and without spinal fusion.

OUTCOME MEASURES

Cyst recurrence and Kawabata, Macnab, Prolo, or Stauffer pain scales.

METHODS

We performed a systematic literature review of all articles published between 1970 and 2009 reporting outcomes after surgical management of spinal synovial cysts.

RESULTS

Eighty-two published studies encompassing 966 patients were identified and reviewed. Six hundred seventy-two (69.6%) patients presented with radicular pain and 467 (48.3%) with back pain. The most commonly involved spinal level was L4-L5 (75.4%), with only 25 (2.6%) and 12 (1.2%) reported synovial cysts in the cervical or thoracic area, respectively. Eight hundred eleven (84.0%) patients were treated with decompressive surgical excision alone, whereas 155 (16.0%) received additional concomitant spinal fusion. Six hundred fifty-four (92.5%) and 880 (91.1%) patients experienced complete resolution of their back or leg pain after surgery, respectively. By a mean follow-up of 25.4 months, back and leg pain recurred in 155 (21.9%) and 123 (12.7%) patients, respectively. Sixty (6.2%) patients required reoperation, of which the majority (n=47) required fusion for correction of spinal instability and mechanical back pain. Same-level synovial cyst recurrence occurred in 17 (1.8%) patients after decompression alone but has been reported in no (0%) patients after decompression and fusion.

CONCLUSIONS

Surgical decompression results in symptomatic resolution in the vast majority of patients; however, recurrent back pain occurs in a significant number of patients. Cyst recurrence occurs in less than 2% of patients but has never been reported after cyst excision with concomitant fusion. The lack of cyst recurrence after concomitant fusion supports the need to investigate the value of fusion of the involved motion segment in the treatment of symptomatic synovial cysts of the spine.

Ganglion cyst of the posterior longitudinal ligament causing lumbar radiculopathy

Degenerated conditions such as herniated disc or spinal stenosis are common etiologies of lumbar radiculopathy. Less common etiologies include spinal extradural cyst such as synovial cysts and ganglion cysts. Ganglion cyst of the posterior longitudinal ligament (PLL) of the spine is a rare entity that can result in classical sciatica. Posterior longitudinal ligament cyst has no continuity with the facet joint and has no epithelial lining. Two young male patients presented with unilateral sciatica and were found to have intraspinal cystic lesions causing lumbar radiculopathy. Magnetic resonance imaging demonstrated rounded, cystic lesions (i.e., hypointense on T1- but hyperintense on T2-weighted images) adjacent to minimally dehydrated, nonherniated disc spaces in both cases. These patients underwent posterior decompression and cysts were excised, and their sciatic symptoms were completely resolved. Histological examination showed typical features of ganglion cysts in these cases.

Diagnostic challenge: bilateral infected lumbar facet cysts--a rare cause of acute lumbar spinal stenosis and back pain

Symptomatic synovial lumbar facet cysts are a relatively rare cause of radiculopathy and spinal stenosis. This case and brief review of the literature, details a patient who presented with acutely symptomatic bilateral spontaneously infected synovial facet (L4/5) cysts. This report highlights diagnostic clues for identifying infection of a facet cyst.

Lumbar intraspinal extradural ganglion cysts

The lumbar intraspinal epidural ganglion cyst has been a rare cause of the low back pain or leg pain. Ganglion cysts and synovial cysts compose the juxtafacet cysts. Extensive studies have been performed about the synovial cysts, however, very little has been known about the ganglion cyst. Current report is about two ganglion cysts associated with implicative findings in young male patients. We discuss about the underlying pathology of the ganglion cyst based on intraoperative evidences, associated disc herniation at the same location or severe degeneration of the ligament flavum that the cyst originated from in young patients.

Prevalence and clinical features of intraspinal facet cysts after decompression surgery for lumbar spinal stenosis

Object

Although many cases of primary intraspinal facet cysts in the lumbar spine have been reported, there have only been a few reports of postoperative intraspinal facet cysts in the lumbar spine. The purpose of this study was to investigate the prevalence and clinical features of postoperative intraspinal facet cysts in the lumbar spine.

Methods

Data from 81 patients undergoing microendoscopic posterior decompression to treat lumbar spinal stenosis were reviewed. The development of a postoperative intraspinal facet cyst was observed using MR imaging during 1 year after surgery. If the patient demonstrated a postoperative intraspinal facet cyst, additional MR imaging was performed to evaluate the natural course of the cyst. Furthermore, the authors conducted a comparative evaluation to identify the factors associated with the causes of cyst development.

Results

A postoperative intraspinal facet cyst developed in 7 patients (8.6%) during 1 year after surgery. Spondylotic spinal stenosis, degenerative spondylolisthesis, and degenerative scoliosis were revealed before surgery in 2, 4, and 1 patient, respectively. In 5 patients, the cysts developed within 3 months after surgery. Although 3 patients exhibited symptoms caused by cyst development, all symptoms were relieved by conservative treatment. On radiographic evaluations, postoperative segmental spinal instability, including a progression of spondylolisthesis and disc degeneration, was revealed in 6 (86%) of the 7 patients. Spontaneous regression of the cysts was observed in 5 (71%) of these 7 patients. On comparative evaluation of patients with and without postoperative intraspinal facet cysts, the presence of segmental spinal instability before surgery (including degenerative spondylolisthesis) and the appearance of postoperative segmental spinal instability were related to the development of the cysts.

Conclusions

The prevalence of postoperative intraspinal facet cysts, including asymptomatic cysts, was 8.6% during 1 year after decompression surgery for lumbar spinal stenosis. The development of postoperative intraspinal facet cysts was related to the presence of segmental spinal instability before surgery (including degenerative spondylolisthesis) and postoperative segmental spinal instability, including a progression of spondylolisthesis and disc degeneration after surgery. A postoperative intraspinal facet cyst, which can be expected to regress spontaneously with a probability > 50%, should be recognized as one of the postoperative complications of decompression surgery for lumbar spinal stenosis.

Spinal synovial cysts: pathogenesis, diagnosis and surgical treatment in a series of seven cases and literature review

This study is designed based on the retrospective analysis of patients treated in the Neurosurgical Department of two major hospitals and review of the literature. The aim of this study is to evaluate the efficacy of surgery and address controversial issues in the treatment of symptomatic lumbar intraspinal synovial cysts. Spinal juxtafacet cysts (synovial and ganglion cysts) are a rare cause of low back and radicular leg pain. Although the relevant reports in the international literature are increasing, the controversy about conservative versus surgical treatment and the need for concomitant fusion still exists. Data from seven patients (age range 58-69 years, mean age 61 years) with low back and radicular leg pain due to a lumbar facet joint cyst were retrospectively analyzed. Demographic data, cyst level, presence of concomitant local pathology, treatment and results of treatment were recorded. A follow-up of at least 6 months (range 6-48 months) was conducted and results were noted. All patients had back pain, while five also experienced unilateral radicular leg pain and one had bilateral leg pain. One patient had neurogenic claudication. MRI identified the cyst and highlighted underlying pathology in all cases. All patients underwent surgical cyst excision. No fusion was performed. Post-operatively, all patients showed a total resolution of symptoms with sustained benefit at final evaluation. Review of the literature revealed a trend towards surgery, as this is correlated to a more favorable outcome compared with conservative treatment. Fusion should be performed on a case-by-case basis only. Surgery is a safe and effective treatment choice in this increasingly appearing ailment. A prospective, randomized trial should clarify issues under debate.

Synovial cyst of the thoracic spine: case report

Spinal cord compressing syndrome due to synovial cyst (SC) of the thoracic spine is a rare clinic condition. We report a case of SC located in the thoracic spine causing spastic paraparesis in a 14 year-old female patient. The SC was removed thoroughly by laminectomy. The patient had an excellent recovery. The etiological and therapeutic aspects are discussed.

Microdecompression for lumbar synovial cysts: an independent assessment of long term outcomes

Background

Outcomes of surgical intervention for lumbar synovial cysts have been evaluated in the short and intermediate term. Concerns regarding cyst recurrence, the development of late instability at the involved level, and instability/stenosis at adjacent levels (when concomitant) fusion is performed suggest that long term follow-up is needed. This study aims to fill that void.

Methods

Forty-six patients operated by a single surgeon not involved in the study were followed up long term at an average of 9.7 years (range 5 to 22 years) post-operatively. All patients underwent decompression (+/- concomitant arthrodesis in the presence of associated degenerative spondylolisthesis) using the operative microscope for magnification/illumination. Outcomes were assessed using a customized questionnaire evaluating: relief of pain/claudicant symptoms, numbness/parasthesias, and weakness; as well as late onset low back pain, new radicular symptoms, need for additional surgery, and patient satisfaction. Outcomes in patients with or without fusion were compared as well.

Results

87% of patients noted resolution of their pre-operative pain, numbness, and weakness. 28% of patients developed late onset low back pain. 17% developed late onset radicular symptoms in a new nerve root distribution. 15% required subsequent additional surgery. 89% of patients were satisfied with the surgical outcome. No differences were found for any outcome measure between patients undergoing concomitant fusion and those undergoing decompression alone using the two-sample t-test.

Conclusion

This study provides outcome data at an average of nearly ten years post-operative. This information should allow surgeons to provide realistic expectations for their patients regarding outcomes and should enhance the informed consent and surgical decision-making process.

Lumbar juxta-facet cyst after trauma

We report a post-traumatic lumbar facet cyst in which results of magnetic resonance imaging (MRI) performed at the time of injury were available. The patient was a 59-year-old man who presented with severe low back and right leg pain immediately after injury of his sacroiliac region in a traffic accident. MRI at the time of injury revealed high intensity signal change in the right facet joint at L4/5. Re-examination 5 months after the injury with MRI revealed a cyst, which was continuous with the facet joint. Surgical resection of the cyst yielded satisfactory results. We describe detailed MRI findings for this case and review the literature on traumatic juxta-facet cyst in the lumbar spine.

Degenerative Erkrankungen der Wirbelsäule

GOAL

The aim of this article is to describe rare and often unrecognized causes of spinal pain syndromes.

METHOD

Intervertebral disc degeneration frequently appears in early adulthood and can have a symptomatic or asymptomatic course. This article discusses incidence, pathophysiology, imaging, and pain symptomatology involved in the origin of back pain.

RESULTS

Anulus tears are often found in asymptomatic individuals but could be implicated in lumbar pain symptomatology in correlation with the provocative discography. Transient disorders can lead to pseudarthrosis of the iliac bone and to degeneration or to a reactive hypermobility with intervertebral disc degeneration in the level above. Modic type 1 erosive osteochondrosis is characterized by bone marrow edema near the hyaline cartilage end plate, which mostly elicits severe pain and results in serious limitations in everyday activities. The most important differential diagnosis is spondylodiscitis. Schmorl's nodes can exhibit considerable surrounding bone marrow edema that can be mistaken for metastases. A combination of MRI and CT should be employed for the diagnostic work-up of fatigue fracture of the interarticular portion, which is often overlooked due to its location. Synovial cysts of the facet joints can lead to radicular symptoms. Insufficiency fracture of the sacrum is frequently mistaken for metastasis due to intense scintigraphic enhancement and its signal behavior in MRI. CT provides instructive information.

CONCLUSION

Differential diagnosis should include less common causes such as anulus tears, transient disorders, activated Schmorl's nodes, synovial cysts of the facet joints, fatigue fractures of the interarticular portion of the spine and the sacrum and distinguish from metastases in particular.

Lumbar hemorrhagic synovial cysts: diagnosis, pathogenesis, and treatment. Report of 3 cases

BACKGROUND

To define the etiologic, clinical, histological, and surgical features of lumbar hemorrhagic synovial cysts (LHSCs). Three personal cases are reported together with a review of the pertinent literature.

METHODS

We identified 3 cases of LHSC treated in our departments and 20 cases culled from the literature.

RESULTS

A total of 23 cases of LHSC were selected. All the patients underwent surgical treatment because of untreatable radicular pain and/or neurological deficits. The amount of bleeding, either massive or minor but repeated, influenced the timing of surgery. In our cases, the histological examinations showed an inflammatory reaction within the cyst and the consequent formation of neoangiogenic vessels.

CONCLUSIONS

Hemorrhagic synovial cyst of the spine is rare and its most common localization is lumbar. Bleeding within the cyst leads to an increase of its volume, accompanied by neurological deficits and/or painful symptoms that are violent and generally intractable. In this event, surgical excision is the treatment of choice and, in some cases, emergency surgery is necessary. Hemorrhages are probably caused by the rupture of fragile neoangiogenic vessels.

Treatment of lumbar synovial cysts using minimally invasive surgical techniques

OBJECT

Lumbar synovial cysts are a potential cause of radiculopathy and back pain, and the definitive treatment is the complete excision of the cyst. This report summarizes the authors' preliminary clinical experience with the minimally invasive resection of lumbar synovial cysts.

METHODS

Nineteen patients (nine men and 10 women) with symptomatic synovial cysts underwent minimally invasive resection. The mean patient age was 64 years of age (range 43-80 years). The presenting symptom was radiculopathy in 16 patients, low-back pain in two, and lower-extremity weakness in one. There were 16 cases of a cyst located at the L4-5 level, two at L3-4, and one at L5-S1. The mean cyst diameter was 13.7 mm (range 3-30 mm). The mean follow-up time was 16 months (range 4-29 months). Clinical outcomes were graded, based on the Macnab modified criteria, as excellent, good, fair, or poor. Eighteen patients (95% of cases) reported either excellent (10 patients) or good (eight patients) results, and a fair result was reported by one patient (5% of cases). The mean operative time was 158 minutes (range 75-270 minutes), and the average intraoperative blood loss was 31 ml (range 10-100 ml). Two patients had intraoperative dural tears that resulted in cerebrospinal fluid leaks that resolved following primary closure.

CONCLUSIONS

Synovial cysts can be safely and effectively treated using minimally invasive surgical techniques. Long-term follow up is required to determine whether this approach results in less need for fusion than conventional surgical approaches.

Spinal lumbar synovial cysts. Diagnosis and management challenge

Sophisticated and newer imaging capabilities have resulted in increased reporting and treatment options of spinal lumbar synovial cysts (LSS). Most of the patients with lumbar cysts tend to be in their sixth decade of life with a slight female predominance. The incidence of LSS is thought to be less than 0.5% of the general symptomatic population. They may be asymptomatic and found incidentally or the epidural growth of cysts into the spinal canal can cause compression of neural structures and hence associated clinical symptoms. Most of the symptomatic LSS patients present with radicular pain and neurological deficits. Spinal synovial cysts are commonly found at L4-5 level, the site of maximum mobility. They may be unilateral or bilateral and at one or multilevel. MRI is considered the tool of choice for its diagnosis. The etiology of LSS is still unclear, but underlying spinal instability, facet joint arthropathy and degenerative spondylolisthesis has a strong association for worsening symptoms and formation of spinal cysts. Synovial cysts resistant to conservative therapy should be treated surgically. Resection and decompression with or without fusion and instrumentation remains an appropriate option. Synovial cysts may recur following surgery. The optimal approach for patients with juxtafacet LSS remains unclear. The best surgical treatment option for each particular individual should be tailored depending upon the symptoms, radiological findings and other co morbidities.

Procedure-based nonsurgical management of lumbar zygapophyseal joint cyst-induced radicular pain

OBJECTIVE

To evaluate the success of fluoroscopically guided, contrast-enhanced lumbar zygapophyseal joint (Z-joint) aspiration and steroid injection combined with transforaminal epidural steroid injections (TFESIs) for the treatment of lumbar Z-joint cyst-induced radicular pain.

DESIGN

Retrospective case series with independent follow-up.

SETTING

Institutional, referral center.

PARTICIPANTS

Twenty-three patients referred to a single provider for procedure-based management of radicular pain believed secondary to lumbar Z-joint cyst. Inclusion criteria consisted of lumbar radicular pain that was consistent with the level and side of the Z-joint cyst as a causative lesion.

INTERVENTIONS

Eighteen patients were treated with a fluoroscopically guided, contrast-enhanced Z-joint aspiration and steroid injection at the level of the causative cyst coupled with a fluoroscopically guided, contrast-enhanced TFESI over the level of the presumably irritated spinal nerve.

MAIN OUTCOME MEASURES

Patient satisfaction, and whether or not surgery was performed.

RESULTS

Fifty percent of patients treated with the procedure had significant long-term benefit and avoided surgical intervention at an average follow-up of 9.9 months.

CONCLUSIONS

Fluoroscopically guided, contrast-enhanced spinal procedures as part of an aggressive nonsurgical treatment program are a safe and effective alternative to surgical intervention for lumbar Z-joint cyst-induced radicular pain.

Ligamentum flavum cysts causing incapacitating lumbar spinal stenosis

BACKGROUND

Cysts of the ligamentum flavum are rare and unusual causes of spinal compression.

METHODS

We report our experience of four cases of ligamentum flavum cysts occurring in the lumbar spine and discuss some of the possible etiologies and pathophysiologic mechanisms according to the available literature.

CONCLUSION

This entity is clearly different from the synovial facet-joints or ganglion cysts.

Epidural hematoma secondary to a rupture of a synovial cyst

BACKGROUND CONTENT

With modern advances in imaging studies, synovial cysts are becoming more evident as a common component of erosive lumbar degenerative disc disease causing spinal stenosis and radiculopathy. Whereas hemorrhage can occur inside the cyst and is reported, rupture causing epidural hematoma is a rare complication and finding of this disorder.

PURPOSE

To report a rare clinical presentation of a synovial cyst and spinal stenosis, where rupture of the cyst leads to an early cauda equina syndrome.

STUDY DESIGN

Case report with a review of literature.

METHODS

Clinical history, physical findings, and magnetic resonance imaging studies of a patient with an intraspinal synovial cyst at L4-5 1 week before a sudden worsening of symptoms are reported.

RESULTS

A case report is presented of a male with a known synovial cyst at L4-5, presenting initially with neurogenic claudication. This patient developed sudden worsening of symptoms with bilateral lower extremity pain, weakness, and radiculopathy with difficult voiding. The patient had developed an epidural hematoma, secondary to rupture of a synovial cyst, documented at surgical decompression.

CONCLUSIONS

Although synovial cyst associated with erosive facet and erosive degenerative disc disease are common, rupture of the cyst is not. A case report of a ruptured synovial cyst leading to an early cauda equina syndrome is presented. This case illustrates the spectrum of clinical features and presentations possible with spinal stenosis complicated by lumbar synovial cyst formation.

Synovial cysts of the thoracic spine

OBJECT

Thoracic synovial cysts (TSCs) are rare and are usually the subject of case reports. The authors studied the clinical manifestations, radiological aspects, and surgical treatment in a series of patients at their institution who harbored TSCs. They also review the literature to discuss the potential factors involved in the pathogenesis of this lesion.

METHODS

A database search of 16,000 patients who underwent decompressive spine surgery at the Mayo Clinic (Rochester, MN) between 1976 and 2003 disclosed nine patients (0.06%) in whom a diagnosis of TSC had been made. All patients were men. The mean age at presentation was 73 +/- 5 years and mean duration of symptoms was 5 +/- 3 months. The mean duration of follow up was 4 +/- 3 years. The patients had no history of trauma or spine surgery. All patients had spastic paraparesis; two had urinary difficulties. Detailed neurological examination revealed myelopathy and radiculopathy with a sensory level of T10-L4. Magnetic resonance imaging revealed bilateral cysts in four patients and unilateral lesions in five. Three of the cysts were at the T-10 interspace, seven at the T-11 interspace, and three at the T-12 interspace. Seven cysts were on the right and six were on the left. Computerized tomography myelography performed in five patients revealed a gas bubble in the TSC in two patients. All patients underwent laminectomy/partial facetectomy, excision of the cyst, and decompression of the thecal sac and nerve root without any complications. None of these patients underwent a fusion. Eight patients (89%) experienced moderate to excellent relief of their preoperative signs and symptoms and one patient (11%) remained stable. There was no evidence of cyst recurrence at the site of surgery or other spinal segments at follow-up examination in any patient.

CONCLUSIONS

When compared with their lumbar and cervical spine counterparts, TSCs are exceedingly rare. Their rarity may be explained by the decreased mobility of the thoracic spinal segments. The origin of TSCs is more likely degenerative rather than traumatic. Based on their experience and the follow-up duration, surgery provided durable relief from symptoms.

Trauma as a precipitant of haemorrhage in synovial cysts

Synovial cysts have been well reported as a cause of sciatica, with a sudden acute exacerbation being attributed to haemorrhage and subsequent enlargement of the cyst. Cyst formation is attributed to facet joint degeneration associated with a defect or rupture of the joint capsule. The mechanisms of haemorrhage have not been well described previously. Two cases of haemorrhagic synovial cysts causing acute exacerbation of sciatica are described. Both cases were directly attributable to manipulation of degenerate spines. The MRI and histopathological findings are discussed and we propose a mechanism whereby excessive stress on a degenerate revascularized synovium leads to haemorrhage within synovial cysts.

Extradural spinal synovial cysts in nine dogs

Nine dogs presenting for investigation of cervical or thoracolumbar myelopathies were diagnosed with extradural spinal synovial cysts. Degenerative disease affecting the articular facets or intervertebral discs was present on plain spinal radiographs in all cases. Myelography was consistent with dorsolateral, extradural spinal cord compression. Two groups of dogs were identified: (1) young, giant breed dogs with multiple cysts involving one or more levels of the cervical spinal cord; and (2) older, large breed dogs with solitary cysts involving the thoracolumbar spinal cord. The synovial cysts constituted the major compressive lesions in four of the dogs. Analysis of lumbar cerebrospinal fluid demonstrated albuminocytological dissociation, consistent with chronic compressive myelopathy, in six dogs. All dogs underwent decompressive surgery and the diagnosis of synovial cysts was confirmed histologically. The mean follow-up period was 17 months (range four to 36 months). At the time of follow-up, all dogs were fully ambulatory with improved neurological function compared with that at initial presentation.