Cauda equina syndrome following vaginal hysterectomy in lithotomy position: A case report

INTRODUCTION

Cauda equina syndrome (CES) is an emergent condition, commonly attributed to an acute lumbar disc prolapse.^[1] Other causes that can increase pressure over the cauda equina include retropulsion of fracture fragments, complications with spinal anesthesia, and epidural abscesses. Pre-existing spine conditions such as degenerative discopathy, spondylolisthesis, facet arthropathy, and thickened ligamentum flavum can lead to spinal canal stenosis and predispose them to CES. In these patients, prolonged abnormal posture or trivial falls can cause sudden pressure on the nerve roots, leading to edema or hematoma formation. CES is a rare surgical emergency that warrants urgent diagnosis and treatment to prevent severe complications that can adversely affect a patient’s quality of life, with high medicolegal implications.^[1] Permanent dysfunctions can be expected in patients who are left untreated or if management is delayed. We present an atypical presentation of CES, which developed following a vaginal hysterectomy in the lithotomy position, only the second such case reported in the literature. We intend to highlight the extremely rare but potentially devastating possibility of cord compression in patients undergoing such procedures, especially those with existing spinal pathology.

CASE REPORT

A 66-year-old female presented to her gynecologist with urinary stress incontinence, nocturia, and recurrent urinary tract infection for 2 years. It was discovered that she had a rectal mass, which was identified as Grade 2 uterine prolapse. She also had a 30-year history of Meyerding I L4/L5 and L5/S1 spondylolisthesis with only intermittent back pain and no neurological deficits. The patient had no other medical or neurological conditions, including diabetes mellitus. She underwent a nearly 4-h vaginal hysterectomy in lithotomy position under general anesthesia with no intraoperative complications. Standard operative protocol related to positioning was adhered to. Histopathological results showed benign findings, as explained to the patient. Following the surgery, she developed severe perineal numbness, saddle anesthesia, painless perineal ulcers, and intermittent urethral burning pain. These post-operative complaints were regarded as being the result of her urogynecology procedure and thus managed conservatively.

Her condition remained unattended and undiagnosed as an orthopedic problem until 3 months later, when fecal incontinence prompted further re-evaluation. Clinical examination revealed reduced sensation in the perianal, gluteal, and posterior thigh areas, lax anal tone, and hyporeflexia of lower limbs but normal motor strength. Magnetic resonance imaging findings showed Meyerding I anterolisthesis at L4/L5 and L5/S1 with ligamentum flavum hypertrophy and facet joint hypertrophy over L3/L4, L4/L5, and L5/S1. There was significant spinal canal narrowing from L3 to S1 levels, leading to nerve root crowding [Figures 1-3].

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Figure 1:

A case of a 66-year-old woman presenting with cauda equina syndrome following vaginal hysterectomy. (a) Pre-operative anteroposterior and (b) lateral radiographs showing the degree of L4/L5 and L5/S1 spondylolisthesis (red arrows).

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Figure 2:

A case of a 66-year-old woman presenting with cauda equina syndrome following vaginal hysterectomy. (a-c) Sagittal T2-weighted magnetic resonance imaging demonstrating Meyerding Grade I anterolisthesis at L4/L5 and L5/S1 (white arrows).

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Figure 3:

A case of a 66-year-old woman presenting with cauda equina syndrome following vaginal hysterectomy. (a-c) Axial T2-weighted magnetic resonance imaging demonstrating spinal stenosis with nerve root overcrowding (white arrows).

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With a diagnosis of CES, the patient underwent urgent posterior lumbar decompression with interbody fusion surgery. This involved directly decompressing the spinal canal with L4 and L5 laminectomies and flavectomy of L3/L4, L4/L5, and L5/S1, and posterior lumbar interbody fusion using iliac bone grafting at levels L4, L5, and S1 [Figure 4].

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Figure 4:

A case of a 66-year-old woman presenting with cauda equina syndrome following vaginal hysterectomy. (a) Post-operative anteroposterior and (b) lateral radiographs showing interbody fusions at levels L4, L5, and S1.

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There was no new neurological deficit after the surgery. Over time, her fecal incontinence resolved. Serial examinations noted a tighter anal sphincter tone as compared to before surgery. The burning sensation over her urethra and numbness were improved gradually. Currently, she is on regular clean intermittent self-catheterization and bladder training to improve her urinary function. Despite the significant delay, the comprehensive surgical intervention addressed her neurological deficits and structural spinal abnormalities, and her neurological recovery is still in progress at 6 months’ follow-up.

DISCUSSION

CES is a rare orthopedic emergency with an estimated incidence of approximately 1 in 33,000–1 in 100,000.^[1] One of the most devastating effects of an improperly diagnosed CES is the possibility of persistent neurological deficit; hence, the urgency in both identifying patients presenting with CES and initiating prompt treatment.

Following this patient’s vaginal hysterectomy, her neurological symptoms were initially dismissed as a transient consequence of the procedure, leading to a delay in diagnosis and treatment. Classical red flag symptoms of perineal numbness and fecal incontinence prompted the patient’s re-evaluation. We postulate that her prolonged surgery (more than 3 h) in a lithotomy position may have caused enough stress on the lumbosacral region to tip the balance toward CES.

It has been established that patients with spondylolisthesis have a reduced spinal canal volume in the affected area compared to normal subjects, and that this volume further decreases when the patient is upright and in extension.^[2] In the lithotomy position, although the patient may be supine, hip and knee flexion, coupled with a tilting of the pelvis, may reverse the lumbar lordosis. This may be exacerbated if a patient’s hips have been hyperflexed. It is possible that overzealous hip flexion during the gynecological procedure may have tilted the pelvis and forced the slipped segment into extension, further compromising the canal volume and resulting in her post-operative presentation. This is our postulation, as definitive data relating to biomechanical changes during the lithotomy position is lacking. In one of the classic studies conducted in 1970, Nachemson and Elfström measured intradiscal pressures during various postures and exercises; however, this did not include a position resembling lithotomy.^[3] Regardless, extrapolating their results, we can infer that being in the lithotomy position, particularly over prolonged periods, may increase anterior disc compression, causing it to bulge into an already restricted spinal canal space.

Gleave and Macfarlane discussed the different clinical presentations of CES and classified them as either CES incomplete or those having CES retention (CESR), and how they relate to surgical outcome.^[4] In a later review, Lavy et al. proposed three additional subclasses.^[5] Based on these categorizations, we suspect that our patient most likely fell into the CESR category because of her fecal incontinence and completely insensate perineum. Despite the worse prognosis in patients with CESR, surgical decompression was attempted.

We could only find a limited number of similar cases reported in the literature. Garry et al. reported an acute case of CES following an abdominal hysterectomy under general anesthesia.^[6] Similar to our case, their patient had an existing slippage of the lumbosacral spine, had been placed in lithotomy position, and had endured a prolonged operative time under general anesthesia. The authors, however, did not venture possible mechanisms to explain the pathology.

Choudhari et al. reported on an acute intervertebral disc prolapse in a patient with a pre-existing canal stenosis who similarly underwent vaginal hysterectomy and presented thereafter with bilateral sciatica with lower limb numbness and attained significant relief with decompression surgery.^[7] Singh et al. described two cases of acute lumbar disc prolapse in their report.^[8] Both patients underwent vaginal hysterectomy in lithotomy positions under spinal anesthesia. In their patients, both recovered with conservative measures. Like us, the authors postulated that manipulation of the patient in lithotomy position with the hips abducted and flexed likely resulted in a disc prolapse. Their patients, however, presented with radiculopathy rather than CES like ours did.

It is known that lithotomy positions may result in several neurological complications, and these are generally compressive and/or traction injuries in the form of neuropraxia, in which recovery is expected.^[7,8] Flanagan et al. had previously explained this traction injury mechanism in their description of their own cases.^[9] The use of regional anesthesia itself could have a role in producing post-operative neurological complications. Intracanal broaching for anesthesia might precipitate CES for such reasons as an inappropriately placed catheter.^[1] However, our patient underwent a vaginal hysterectomy under general anesthesia, making this case unique. Her spondylolisthesis remained unchanged at Meyerding grade 1 before and after her hysterectomy and had been stable without neurological symptoms for decades. It is unlikely that the cauda equina presentation is due solely to the listhesis, as the risk for such occurrence is generally low.^[10] The stress incontinence that the patient had before surgery is most likely related to her uterovaginal prolapse rather than spinal cord compression, as no other manifestations were present.

None of the authors cited above was able to provide conclusive evidence as to the cause of their patients’ post-operative symptoms. We are only able to postulate our conclusions based on the timing of the symptom presentation, absence of other causes, and inference from available data, although indirectly related. Being such a rare occurrence, we would require either further cadaveric or computer modelling to procure a definite date. We propose, based on these observations, that positioning during surgery might be implicated in this patient’s symptoms. Due to the rarity of this type of complication, it is difficult to ascertain whether a pre-operative orthopedic consult would have altered the outcome. However, extra vigilance to positioning could have been exercised, and more importantly, earlier identification and management of the CES could have been made.

Due to the retrospective nature of the diagnosis, our inability to identify a direct causality is a limitation. Given the history, radiological and operative findings, and post-operative improvement, a posture-related exacerbation of the spinal pathology is the most likely mechanism. We would need further biomechanical and modelling studies to verify this.

CONCLUSION

This rare case highlights a potentially devastating complication of CES in a patient with pre-existing spinal pathology undergoing procedures in the lithotomy position. The postulated mechanism discussed suggests that this complication is not limited to gender. It underscores the importance of pre-operative planning, proper positioning, and post-operative cognizance in such patients, particularly those undergoing prolonged procedures. The hazards involved may result in long-standing, even permanent, debilitating consequences, particularly urogenital complications. Given the morbidity and medicolegal implications, we therefore recommend a detailed work-up and urgent orthopedic consultation in patients presenting with similar post-operative complaints. Future research, including biomechanical modelling, may help shed more light on the precise mechanism and risks associated with the lithotomy position in at-risk patients.