Paraspinal desmoid fibromatosis after lumbar epidural analgesia

Abstract

A 14‐year‐old girl with cerebral palsy presented for bilateral lower limb surgery for spasticity. A lumbar epidural catheter was sited under general anaesthesia on the third attempt and used intra‐operatively with good effect. A local anaesthetic infusion was used for postoperative analgesia but was noted to be leaking under the dressing with a patchy, unilateral block. The catheter was therefore removed on the second postoperative day. Following discharge, the patient progressively developed new back and leg pain for which she was re‐admitted seven weeks later. This was investigated and initially thought to be myositis of the erector spinae muscles on magnetic resonance imaging. When the patient failed to respond to treatment, a muscle biopsy demonstrated desmoid fibromatosis. Trauma may cause or accelerate the development of desmoid fibromatosis, which has also been theorised to arise from scar tissue in previously injured areas. We hypothesise that challenging epidural placement or the leakage of the local anaesthetic agent into the surrounding muscular tissue, inducing local myonecrosis, could have been the triggering or accelerating event in tumour development. This may be the first reported case of extra‐abdominal desmoid fibromatosis in association with epidural placement.

Introduction

Desmoid tumours are rare, benign tumours that have the potential to cause significant morbidity and mortality. Spinal desmoid tumours are even rarer and, due to their proximity to the neural tissues and spinal canal, have a greater risk of significant complications. Usually sporadic in nature, they have also been known to occur due to genetic causes and trauma including surgery but have not previously been associated with neuraxial analgesia. In this report, we describe a case of a desmoid tumour with a temporal relationship to the placement of a lumbar epidural catheter and potential myositis due to local anaesthetic leakage.

Report

An ex‐premature (born at 27 weeks’ gestational age) 14‐year‐old girl with diplegic cerebral palsy underwent orthopaedic surgery involving bilateral semitendinosus transfer and gastrocnemius release. She had mixed motor‐type cerebral palsy (dyskinetic and spastic) accompanied by complex partial seizure disorder. There were no known spinal issues nor clinically apparent scoliosis.

Following inhalational induction of general anaesthesia, a senior anaesthetic trainee performed an epidural at the L4/5 interspace in the lateral position under full aseptic technique. Following some difficulties in locating the midline, loss of resistance to saline was achieved on the third attempt at a depth of 4.5 cm. The epidural catheter was secured at 8 cm at the skin. An initial bolus of 10 ml ropivacaine 0.2% was given with hourly boluses repeated throughout the operation. Postoperatively, an infusion of levobupivacaine 0.125% was commenced at 15 ml.h^‐1. The patient was comfortable in the post‐anaesthesia care unit with a sensory block to ice to the L1 dermatome on the right and L2 on the left. Later that evening, she complained of pain, and on assessment, there was reduced epidural coverage on the right and fluid accumulation was noted beneath the dressing. The dressing was reinforced, and the epidural infusion continued. On the second postoperative day, there was no sensory block to ice on the right and a block to the L2 dermatome on the left. The fluid accumulation persisted despite dressing reinforcement, and in the setting of the partial analgesic effect, the epidural catheter was therefore removed. There were no further concerns regarding the epidural site following removal and no complaints of back pain. The remainder of the patient’s hospital stay was uneventful.

Two weeks following discharge, the patient complained of mild backache but had weaned off analgesics and was tolerating physiotherapy. This pain, in the right paraspinal area at the level of L4 and L5, progressively worsened and became radicular. She remained systemically well, but the pain persisted, and she was therefore re‐admitted for investigation seven weeks following surgery. There was no increase in inflammatory markers and blood cultures were negative. Ultrasound imaging demonstrated a right paraspinal and erector spinae muscle abnormality, measuring 128 × 31 × 20 mm, suggestive of a resolving haematoma or collection. She subsequently underwent magnetic resonance imaging (MRI) which showed right‐sided paraspinal muscle oedema signal pattern on T2‐weighted images and gadolinium contrast enhancement on T1‐weighted images, from the level of L2 to S2. These findings were thought to be suggestive of infection with no epidural abscess or indication of osteomyelitis (Fig. 1a). Diagnoses of epidural‐related infection or local anaesthetic‐induced myositis were considered, and intravenous antibiotics were commenced. Following only mild symptomatic improvement, the patient underwent repeat MRI two weeks later. This imaging demonstrated persisting severe oedema and enhancement of the right erector spinae musculature with some small curvilinear non‐enhancing areas (Fig. 1b). Given the lack of radiological progress or clinical markers of infection, a muscle biopsy was performed, demonstrating low‐grade sclerosing myofibroblastic proliferation without myonecrosis or myositis. No pathogenic micro‐organisms were identified on special stains and immunohistochemical staining of the spindle cell proliferation showed diffuse positive cytoplasmic smooth muscle actin and calponin positivity, with focal desmin staining. A right paraspinal desmoid type fibromatosis was diagnosed. Following multidisciplinary team review, surgery was not advised, and she was commenced on oral pazopanib. Her symptoms improved with surveillance MRI demonstrating improvement and regression of T2 signal abnormality (Fig. 1c).

Figure 1.

Magnetic resonance imaging (T2 weighted and T1 weighted with gadolinium contrast) demonstrating (a) initial progression, and subsequent regression following treatment at (b) three and (c) nine months postoperatively. Arrows demonstrate oedema and contrast enhancement of right paraspinal musculature

Discussion

This is a rare case of a spinal desmoid tumour that may have been unmasked or triggered by the insertion of an epidural or local anaesthetic‐induced muscle injury to the erector spinae muscles. Originally described in the 1830s, desmoid tumours are benign, rare, exuberant fibroblastic proliferations arising in deep soft tissues [1]. They are slow growing, but locally aggressive, and possess a tendency towards recurrence but an inability to metastasise [1]. Their incidence is two to six cases per million per annum with spinal presentations of fibromatosis even rarer [1, 2]. Desmoid tumours originate from deep musculo‐aponeurotic structures and can cause pain through compressive effects and local infiltration of adjacent structures. There is a female predominance of around 2:1, and they most typically occur between the ages of 15 and 60 y [3, 4]. Thought to be mostly sporadic in nature, risk factors include a genetic predispositions in the setting of familial adenomatous polyposis, pregnancy, oral contraceptive use and trauma, potentially as a result of surgical procedures [2].

Desmoid tumours arising within scar tissue or in previous tissue injury locations have been theorised to result from an abnormal response to healing with persistent immature fibroblast formation giving rise to the tumour [5]. A previous case series of spinal fibromatosis indicated an equal distribution for association with trauma (45%) and de novo occurrences (45%), with the remainder from genetic causes [6]. In this patient, the genetic sequencing panel did not identify the CTNNB1 gene or adenomatous polyposis coli abnormalities, indicating a non‐genetic desmoid tumour [7]. It is possible, considering the challenging epidural placement in this case, that the repeated attempts and a potentially excessive lateral needle position may have caused local trauma to the paraspinal musculature as the potential triggering event. Additionally, despite no previous reported cases of myositis or necrosis as a result of local anaesthetic agents causing desmoid tumours, leakage of the local anaesthetic agent into the muscle tissue could have induced myonecrosis and subsequent inflammation, accelerating or triggering tumour development within the erector spinae muscles.

Although uncommon, local anaesthetic drugs can cause skeletal muscle injury with the extent of muscle damage dependent on dose and volume [8]. This can occur with continuous administrations and at clinically used concentrations. A systematic review of over 50,000 patients found that the incidence of myotoxic damage was 0.77% with increased concentrations and duration of exposure associated with greater muscle damage [9]. In this case, the patient had around 40 h of levobupivacaine 0.125% at 15 ml.h^‐1 and given the fluid accumulation noted around the dressing some may have leaked into the paraspinal muscles, provoking an inflammatory response. Of note, the biopsy eight weeks later did not demonstrate myonecrosis or myositis, perhaps making this less likely.

Despite their benign microscopic appearance, desmoid tumours have the potential to locally infiltrate, risking significant deformity, morbidity and mortality. Spinal desmoids pose a relatively greater risk due to their close proximity to neural structures and the spinal canal [5]. The differential diagnosis includes malignancy which makes a biopsy essential [4]. Once identified, MRI is the imaging modality of choice for evaluation and ongoing surveillance of the lesion and its impact on anatomical relations. This in turn determines the optimal treatment pathway [3, 5]. The course of desmoid tumours is unpredictable with a large variation in their natural history with some progressing rapidly and others regressing spontaneously [4, 10]. Invasive surgical treatment is used with caution due to the potential for recurrence, irrespective of the margin status. Management is best approached with involvement of a multidisciplinary team, considering the risks and benefits of surgery, observation, radiotherapy, chemotherapy, hormonal and anti‐inflammatory therapy [2, 3, 10]. Oral pazopanib is a novel oral tyrosine kinase inhibitor licenced for soft tissue sarcomas and has shown some promise in aggressive desmoid tumours; this case further supports its use in appropriate patients [1].

Desmoid tumours can occur in association with trauma but their aetiology is primarily sporadic. Although this tumour may have been pre‐existing but asymptomatic in this patient, or a simple coincidence, it is also possible that it was accelerated or triggered by the presence of epidural analgesia. This is the first reported case of a desmoid tumour with a temporal association to epidural analgesia.