A Tiny Hole with Big Consequences

A 14-month-old girl with a history of sacral dimple with cutaneous nevus simplex is brought to the emergency department by her mother for multiple episodes of nonbilious, nonbloody emesis; inability to tolerate oral intake; and 1 episode of watery, nonbloody diarrhea on the day before presentation. There have been no subsequent stools. One month earlier, she presented to the emergency department with a history of fever and purulent drainage from the sacral dimple. At that time, she was treated with an oral clindamycin course for presumed localized cellulitis.Review of systems is positive for intermittent abdominal pain and negative for any recent illness, fever, weight changes or skin rashes aside from cellulitis 1 month earlier. The patient was born at 40 weeks’ gestation with an uneventful nursery course and has attended routine health maintenance visits. She has normal growth velocity and is able to crawl, stand, and bear weight. She cruises but does not walk independently. Her caregiver reports that the sacral dimple has been present since birth, but no imaging has been performed. The dimple has been stable and asymptomatic until the recent emergency department visit. There are no sick contacts at home and no pertinent family history.Initial physical examination reveals vital signs within normal limits for age: temperature, 98.4°F (36.9°C); heart rate, 132 beats/min; and respiratory rate, 34 breaths/min. She is nontoxic-appearing, alert, and playful. She has moist mucous membranes. Cardiopulmonary examination findings are normal. Her abdomen is distended, with a palpable, tender suprapubic mass suggestive of distended bladder. She has a painless, nonmobile, indurated lesion with a central dimple in the sacral area with overlying erythema of the skin consistent with nevus simplex.Initial laboratory data show a complete blood cell count, complete metabolic profile, and C-reactive protein (CRP) within normal limits. She has a negative respiratory pathogen panel polymerase chain reaction. The erythrocyte sedimentation rate (ESR) is elevated to 30 mm/hr (reference range, 0–20 mm/hr). Urinalysis shows ketones (20 mg/dL) (reference range, negative). Urine and blood culture samples are collected. Her abdominal radiograph shows mild to moderate stool burden. Abdominal ultrasonography shows a markedly distended bladder measuring 10 × 5.5 × 9 cm, with bilateral hydroureteronephrosis. Bladder catheterization is performed, resulting in approximately 300 mL of urine. She is admitted to the floor for further management.On subsequent evaluation, she is noted to have bilateral lower extremity hypotonia, which progresses to hyperreflexia and bilateral clonus at knee level with absence of anal tone. Ultrasonography of the lumbar spine shows subcutaneous hypoechoic lobular lesions measuring 14 × 5×13 mm, with a tract extending to the skin surface (Fig 1). Acute abdominal pain and vomiting can be secondary to numerous etiologies; however, the presence of a sacrococcygeal cutaneous lesion with dimple, acute urinary retention, constipation, and neurologic changes raises the suspicion for spinal cord pathologies. Additional imaging confirms the diagnosis.Magnetic resonance imaging (MRI) of the spine reveals cervical and thoracic central syrinx and a sinus tract with a dorsal defect in the osseous spinal canal at S2-S3. There is a nonenhancing cystic component in a tethered cord and enhancement of the cord at L1-L2 extending into the sacral spinal canal with surrounding edema (Fig 2). These findings are consistent with an infected congenital inclusion cyst with a tethered cord.Sacral dimples or pits can be identified in 2% to 4% of newborns and are common, benign congenital variants that are usually single, with a well-visualized base and a small size (<5 mm) located less than 25 mm above the anal opening. (1) Differentiating benign lesions from occult spinal dysraphism (OSD) is imperative to avoid complications. OSD disorders are associated with midline defects of vertebral bodies, without obvious extension of the spinal cord or meninges through the defect. (2)(3) Dimples or pits can provide indirect evidence of OSD (2) and can present with other cutaneous stigmata (pigment changes, nevi, hemangioma, hairy patch), subcutaneous swelling, or signs of local infection (drainage of debris/pus) in 86% of cases. (4)(5)Most patients with OSD are asymptomatic without consequences, (2) but occasionally abnormalities involving sacral structures and/or the spinal cord are present, such as syringomyelia, diastematomyelia, lipoma, fatty filum, congenital dermal sinus (CDS), or tethered cord. (2)(3)(6) Such abnormalities can lead to a wide range of clinical manifestations, including congenital tethered cord syndrome and later-onset complications such as spondylosis, degenerative disc disease, and spinal stenosis, which can present in adulthood. (3)Congenital dermal sinus tracts arise between the second and eighth weeks of fetal development, after aberrant cutaneous and neural ectoderm division, leading to formation of a tract lined by squamous epithelium and dermal cells. (5)(7) CDS can occur anywhere along the craniocaudal axis, with lumbar and lumbosacral locations being most frequent, (5) and the incidence is approximately 1 in 2,500. (8) A midline dimple above the gluteal cleft with or without cutaneous findings may be the only indication of CDS on physical examination. (9) More common diagnoses, such as pilonidal sinus or benign coccygeal dimples, can be confused with CDS, leading to misdiagnosis and delays in appropriate management. (4)Spinal inclusion cysts such as dermoid and less frequently epidermoid are present in almost half of all CDS lesions and can be found at any point along the tract. (5)(6)(10)(11)(12) Clinical presentation of an inclusion cyst is usually due to mass effect, cyst rupture, and/or infective complications, as was present in our case. (11)(12)(13) Unrecognized CDS can be a portal of entry for pathogens to reach the spinal canal, resulting in central nervous system infections, including subdural/spinal intramedullary abscess and meningitis. (4)(14) Toddlers represent 18% of patients presenting with central nervous system infections. (10)Spinal intramedullary abscess in children is a rare diagnosis. (15) Manifestations range depending on size, extent, and location in the spinal cord. (15) Acute cases are associated with fever, backache, elevated white blood cell count, and inflammatory markers (CRP and ESR). (14) Chronic presentation may mimic signs and symptoms of spinal intramedullary tumors without significant elevation of CRP/ESR, leukocytosis, or fever, (16) similar to our case. The most common organisms include Staphylococcus aureus, Escherichia coli, and Proteus mirabilis and, in some cases, can be polymicrobial. (4)(13)(14)(15)The diagnosis of CDS should be suspected in the presence of a midline spinal lesion, where the base cannot be clearly visualized, (10) when it is large (>5 mm), located more than 25 mm from the anal opening, and/or associated with cutaneous findings. (15) When suspected, imaging studies should be ordered to further delineate the lesion. Spinal ultrasonography is a usual initial screening tool in newborns and infants and offers similar sensitivity and specificity compared with MRI. (17)(18) Ultrasonography can yield best results if used after 1 month of age to ensure appropriate view of spinal structures, including the thickness of the filum terminale, (19) but it can be challenging to perform after 3 to 6 months of age, when ossification of the posterior spinal structures minimizes the window view. (17)(19)(20) In contrast to MRI, spinal ultrasonography has the advantages of low cost and ease of performance and coordination, without requiring sedation. (17)MRI is the neurodiagnostic technique of choice in older children (20) or when other cutaneous stigmata and/or abnormal neurologic examination is present (1) as it provides detailed information on the neural structures and their relationship to the dermal sinus tract (4) needed for surgical planning and intervention. (9)The patient’s acute neurologic deficits are secondary to intramedullary abscess expansion. She is started on intravenous antibiotics and subsequently undergoes fenestration of sinus tract, laminectomy, and abscess drainage. Tissue biopsy confirms the diagnosis of infected sacral epidermoid inclusion cyst and dermal sinus tract. Wound culture grows methicillin-sensitive Staphylococcus aureus, and antibiotics are tailored based on sensitivities, with a planned therapy duration of 6 weeks. Repeated spinal MRI reveals interval decrease in size of the intramedullary abscess and edema. At discharge, the patient has resolution of her neurologic symptoms.