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Sciatica: An Extremely Rare Complication of the Perianal Abscess

View Article: PubMed Central - PubMed

ABSTRACT

Background: Sciatica has been classically described as pain in the back and hip with radiation in the leg along the distribution of the sciatic nerve, secondary to compression or irritation of the sciatic nerve. Spinal abnormality being the most common etiology, is one of the most common indications for MRI of the lumbosacral spine. Here we describe imaging findings secondary to a supralevator perianal abscess causing irritation of the sciatic nerve, which was diagnosed on MRI of the lumbosacral spine.

Case report: A 47-year-old male patient presented to the emergency department with severe acute pain in the right hip and right leg which was aggravated by limb movement. Clinically, a possibility of sciatica was suggested and MRI of the lumbosacral spine was ordered. The MRI did not reveal any abnormality in the lumbosacral spine; however, on STIR coronal images, a right perianal abscess with air pockets was seen. The perianal abscess was extending above the levator ani muscle with and was seen tracking along the sciatic nerve, explaining pain along the distribution of the sciatic nerve. The abscess was surgically drained, followed by an antibiotic course. The patient was symptomatically better post-surgery. Post-operative scan done 3 days later revealed significant resolution of the infra- and supralevator perianal abscess. The patient was discharged from hospital on post-operative day 3 on oral antibiotics for 7 days. On 15th post-operative day, the patient was clinically completely asymptomatic with good healing of the perianal surgical wound.

Conclusions: Extra-spinal causes are rare and most often overlooked in patients with sciatica. While assessing patients with sciatica, extra-spinal causes for the radiation of pain along the distribution of the sciatic nerve should always be looked for if abnormalities in the MRI of the lumbar spine are not found. Inclusion of STIR sequences in the imaging of the lumbosacral spine, more often than not, helps to identify the extra-spinal cause of sciatica when MRI of the lumbosacral spine does not reveal any abnormality.

No MeSH data available.


STIR coronal image showing hyperintense signal on the right side of the pelvis (arrow) which is seen extending towards the greater sciatic foramen (arrow heads).
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f1-poljradiol-81-370: STIR coronal image showing hyperintense signal on the right side of the pelvis (arrow) which is seen extending towards the greater sciatic foramen (arrow heads).

Mentions: MRI of the lumbosacral spine was advised for evaluation of the back pain radiating to the right limb. MRI of the lumbosacral spine did not reveal any significant spinal abnormality. However, an abnormal hyperintense signal was noticed in the right gluteal muscles and perianal region on large field of view STIR coronal images (Figure 1). Subsequently, dedicated T2W and T1W images were taken for assessment of the pelvis. A perianal collection with marked T2WI and T1WI hypointensities suggestive of air was noticed (Figure 2). Abnormal STIR hyperintense signals with air pockets were also noted extending into the right greater sciatic notch and along the right sciatic nerve. Additionally, the diffusion weighted sequence was planned and it revealed areas of restriction within the right perianal collection (Figure 3). A CT scan of the pelvis confirmed presence of perianal abscess in the right ischiorectal fossa with multiple air pockets (Figures 2, 4), tracking along the right sciatic nerve up to the mid-thigh. Preoperative evaluation of the patient also revealed high fasting (165 mg/dL) and postprandial (220 mg/dL) blood glucose levels. The right ischiorectal fossa abscess was surgically drained with a drainage tube kept in the ischiorectal fossa. Microbiological examination of the abscess revealed gram-negative rods suggesting Escherichia coli. A postoperative CT scan 3 days later revealed significant resolution of the abscess and the air pockets. The patient was discharged after 3 days of hospitalization on oral antibiotic treatment for gram-negative and anaerobic bacteria for 7 days. On 15th post-operative day, the patient was completely asymptomatic and showed signs of healthy healing of the perianal surgical wound.


Sciatica: An Extremely Rare Complication of the Perianal Abscess
STIR coronal image showing hyperintense signal on the right side of the pelvis (arrow) which is seen extending towards the greater sciatic foramen (arrow heads).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036378&req=5

f1-poljradiol-81-370: STIR coronal image showing hyperintense signal on the right side of the pelvis (arrow) which is seen extending towards the greater sciatic foramen (arrow heads).
Mentions: MRI of the lumbosacral spine was advised for evaluation of the back pain radiating to the right limb. MRI of the lumbosacral spine did not reveal any significant spinal abnormality. However, an abnormal hyperintense signal was noticed in the right gluteal muscles and perianal region on large field of view STIR coronal images (Figure 1). Subsequently, dedicated T2W and T1W images were taken for assessment of the pelvis. A perianal collection with marked T2WI and T1WI hypointensities suggestive of air was noticed (Figure 2). Abnormal STIR hyperintense signals with air pockets were also noted extending into the right greater sciatic notch and along the right sciatic nerve. Additionally, the diffusion weighted sequence was planned and it revealed areas of restriction within the right perianal collection (Figure 3). A CT scan of the pelvis confirmed presence of perianal abscess in the right ischiorectal fossa with multiple air pockets (Figures 2, 4), tracking along the right sciatic nerve up to the mid-thigh. Preoperative evaluation of the patient also revealed high fasting (165 mg/dL) and postprandial (220 mg/dL) blood glucose levels. The right ischiorectal fossa abscess was surgically drained with a drainage tube kept in the ischiorectal fossa. Microbiological examination of the abscess revealed gram-negative rods suggesting Escherichia coli. A postoperative CT scan 3 days later revealed significant resolution of the abscess and the air pockets. The patient was discharged after 3 days of hospitalization on oral antibiotic treatment for gram-negative and anaerobic bacteria for 7 days. On 15th post-operative day, the patient was completely asymptomatic and showed signs of healthy healing of the perianal surgical wound.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Sciatica has been classically described as pain in the back and hip with radiation in the leg along the distribution of the sciatic nerve, secondary to compression or irritation of the sciatic nerve. Spinal abnormality being the most common etiology, is one of the most common indications for MRI of the lumbosacral spine. Here we describe imaging findings secondary to a supralevator perianal abscess causing irritation of the sciatic nerve, which was diagnosed on MRI of the lumbosacral spine.

Case report: A 47-year-old male patient presented to the emergency department with severe acute pain in the right hip and right leg which was aggravated by limb movement. Clinically, a possibility of sciatica was suggested and MRI of the lumbosacral spine was ordered. The MRI did not reveal any abnormality in the lumbosacral spine; however, on STIR coronal images, a right perianal abscess with air pockets was seen. The perianal abscess was extending above the levator ani muscle with and was seen tracking along the sciatic nerve, explaining pain along the distribution of the sciatic nerve. The abscess was surgically drained, followed by an antibiotic course. The patient was symptomatically better post-surgery. Post-operative scan done 3 days later revealed significant resolution of the infra- and supralevator perianal abscess. The patient was discharged from hospital on post-operative day 3 on oral antibiotics for 7 days. On 15th post-operative day, the patient was clinically completely asymptomatic with good healing of the perianal surgical wound.

Conclusions: Extra-spinal causes are rare and most often overlooked in patients with sciatica. While assessing patients with sciatica, extra-spinal causes for the radiation of pain along the distribution of the sciatic nerve should always be looked for if abnormalities in the MRI of the lumbar spine are not found. Inclusion of STIR sequences in the imaging of the lumbosacral spine, more often than not, helps to identify the extra-spinal cause of sciatica when MRI of the lumbosacral spine does not reveal any abnormality.

No MeSH data available.