Novel Insights from Clinical Practice Pediatr Neurosurg 2013;49:360–364 DOI: 10.1159/000368278
Received: April 25, 2014 Accepted after revision: September 7, 2014 Published online: December 17, 2014
Symptomatic Thoracic Arachnoid Cyst with Coexisting Tick Paralysis: Case Report and Review of the Literature Kimberly A. Foster Nathan T. Zwagerman Christian Ricks Stephanie Greene Department of Neurosurgery, Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pa., USA
Established Facts • Tick paralysis is a rare condition which can cause significant morbidity and even death. • Spinal arachnoid cysts are also a rare cause of progressive paralysis.
Novel Insights • Patients can present with multiple underlying etiologies to progressive paralysis. • Tick paralysis must be included in the differential diagnosis of progressive ascending paralysis in children.
Key Words Arachnoid cyst · Thoracic spine · Tick paralysis
Abstract Tick paralysis is an uncommon phenomenon resulting from the release of a neurotoxin from the salivary glands of an engorged, gravid female tick about 5–7 days after attachment. The neurotoxin produces ascending weakness, mimicking other ascending paralytic processes. We present a case of a child presenting with weakness of the lower extremities and frequent falls who was found to have a compressive thoracic arachnoid cyst and a large distal syrinx. After surgical decompression, the patient made significant improvement in
© 2014 S. Karger AG, Basel 1016–2291/14/0496–0360$39.50/0 E-Mail [email protected] www.karger.com/pne
her leg strength, but quickly developed an ascending quadriparesis, followed by respiratory depression. Subsequent imaging and physical examination revealed an engorged tick embedded in her scalp. The tick was removed, and the patient made a rapid and complete clinical recovery. We present a unique case of concomitant tick paralysis and a symptomatic spinal intradural arachnoid cyst, and review the literature on tick paralysis. © 2014 S. Karger AG, Basel
Kimberly A. Foster and Nathan T. Zwagerman shared first authorship of the manuscript.
Kimberly A. Foster, MD Department of Neurosurgery, University of Pittsburgh 4th Floor Faculty Pavilion, 4401 Penn Ave. Pittsburgh, PA 15224 (USA) E-Mail fosterka @ upmc.edu
Tick paralysis is a rare condition which, when overlooked or misdiagnosed, can cause significant morbidity and even death [1]. Most cases occur during the spring or summer months in children younger than 8 years of age [2, 3]. Tick paralysis is more common in girls, possibly due to the length of their hair masking the presence of a tick [4]. The rapidly progressive ascending paralysis is difficult to distinguish from other ascending paralytic diseases such as Guillain-Barré syndrome and poliomyelitis [5]. Treatment primarily consists of removing the tick from the patient, which produces resolution of symptoms in short order [6, 7]. If the tick is not removed, the disease may progress to respiratory arrest and death. Tick paralysis should be considered in any child who has developed a progressive ascending paralysis [3, 5]. Spinal arachnoid cysts are also a rare cause of progressive paralysis [8]. While intracranial arachnoid cysts are identified in 1.7–2.6% of pediatric patients who undergo cranial imaging [9, 10], spinal arachnoid cysts are much less common. These cysts are frequently extradural, dorsal to the spinal cord, and located in the thoracic region [11–13]. They may be congenital (possibly secondary to a widening of the septum posticum [14]) or acquired from inflammation following surgery, meningitis or trauma [15, 16]. Multiple theories regarding the etiology of arachnoid cysts, as well as the impetus for their enlargement over time, have been put forth. A ball valve effect [17–22], the movement of fluid from the subarachnoid space into the cyst due to an osmotic gradient [15, 23, 24] and active secretion from cells lining the cyst [23, 25] have been postulated as mechanisms for cyst enlargement over time. Patients with spinal arachnoid cysts present with back pain and signs of progressive myelopathy, including lower extremity weakness, gait instability, sensory loss, and bowel and bladder dysfunction [16, 26–29]. The association of a syrinx with an intradural arachnoid cyst has been reported in adults [30–32] but was recently reported for the first time in a child [33]. Although both tick paralysis and spinal arachnoid cysts have been cited independently as causes of paralysis in children, this is the first case to our knowledge in which their simultaneous presentation has been reported in the literature.
Case Report
a
b
Fig. 1. MRI of thoracic spine, sagittal images. a Preoperative imaging indicates a dorsal thoracic arachnoid cyst with associated syringomyelia. b Imaging obtained on postoperative day 2 indicates diminished size of both the arachnoid cyst and syringomyelia.
ing and reported that her legs felt ‘wobbly’. In the emergency department, she had the ability to stand with assistance, but refused to stand without assistance. She and her caretaker denied numbness, tingling, or bowel or bladder dysfunction, and reported no recent illness or sick contacts. While tick-borne illnesses are endemic to the region where the child lives, later questioning revealed that she had not recently been outdoors in a known tick-infested area. Her review of systems was unremarkable for fever, rash or other signs of systemic illness. She had no medical or surgical history, was taking no daily medications, and had no known medical or environmental allergies. Complicating her presentation was the fact that she had been with this foster family for only 2 weeks, and there was minimal information regarding her family history. Examination On examination in the emergency department, she was awake, alert and oriented. Her cranial nerves were intact. Upper extremity examination revealed 5/5 strength in all muscle groups, while her lower extremities were 3/5 strength in all muscle groups symmetrically. Sensation was diminished to light touch, proprioception, pain and temperature throughout. Deep tendon reflexes were 2+ in the bilateral upper extremities and 1+ at the patellar and Achilles’ tendons bilaterally. She did not demonstrate ankle clonus or an abnormal plantar response. She was able to bear weight and stand with assistance, though she was unable to stand independently. A 3-tesla MRI with and without the administration of gadolinium was performed through the thoracic and lumbar spine. This indicated a thoracic syrinx extending from T4 to T8, with the greatest diameter measuring 4.5 mm. Dorsal to the C7–T4 levels, an arachnoid cyst was identified to be producing ventral displacement of the cord (fig. 1).
History A 4-year-old female child presented to the emergency department of a large pediatric tertiary care center in May with the onset of progressive lower extremity weakness over the preceding 2 days. She awoke on the day prior to her presentation with difficulty walk-
Operation The patient underwent a T2–T4 laminectomy, midline durotomy and wide fenestration of the arachnoid cyst into the normal surrounding subarachnoid space. The cyst was noted to be under high pressure; the arachnoid membrane of the cyst was found to
Thoracic Arachnoid Cyst and Tick Paralysis
Pediatr Neurosurg 2013;49:360–364 DOI: 10.1159/000368278
361
Color version available online
be opaque and thickened, in contrast to the normal wispy arachnoid. The spinal cord was visualized to be flattened and displaced ventrally. Postoperative Course Postoperatively, the child was extubated in the operating room and documented by the surgical and anesthesia services to be moving her legs spontaneously and symmetrically. On postoperative day 1, the patient developed respiratory distress and required reintubation. At this time, motor strength was full in her arms and 4/5 in her legs. A chest X-ray revealed a pulmonary infiltrate, she was diagnosed with pneumonia, and antibiotic therapy was initiated. Over the ensuing 3 days, the patient failed extubation multiple times. She became gradually weaker during this time, initially in the distal lower extremities and progressing rostrally and her strength deteriorated to 1/5 proximally and 2/5 distally in the bilateral upper extremities, 1/5 in the left lower extremity and 2/5 in the right lower extremity. A repeat MRI including the entire neuraxis indicated near-complete resolution of the arachnoid cyst and syrinx, with expected postoperative changes and no new abnormalities. Due to ongoing paralysis, electromyography and nerve conduction studies were completed. The latter revealed low compound motor action potentials in multiple nerves with preserved sensory nerve action potentials. There was no prolongation in conduction velocity seen, and normal F wave responses were noted, suggesting a diffuse motor axonal neuropathy or a presynaptic neuromuscular junction disturbance. On detailed physical examination of the patient, an engorged tick was noted behind the patient’s left ear and was carefully removed by grasping the tick as closely as possible to its attachment site and using steady traction to ensure the head or mouthparts did not remain engaged, so as to avoid leaving behind neurotoxin still present in the salivary glands. The tick was identified as a gravid female of the Dermacentor species (fig. 2). On further review of the imaging, MRI of the brain revealed an abnormal extracranial mass behind the left ear embedded in the scalp (fig. 3). Within 12 h following tick removal, the child was able to move all extremities against gravity. She had the rapid return of respiratory effort, and was weaned off of the ventilator and extubated approximately 36 h after tick removal. On postoperative day 16, she was discharged to home with outpatient physical therapy. At her initial postoperative visit 3 weeks after surgery, she was neurologically intact and had resumed her baseline activity level.
Fig. 2. Gross pathology specimen of the tick removed from the
child’s scalp, identified as a gravid female Dermacentor variabilis.
Fig. 3. MRI of brain, coronal image. Note identification of an ex-
tracranial lesion found to be an engorged Dermacentor tick, known to produce symptoms of tick paralysis (white arrow).
Discussion
Tick paralysis is a rare entity that can occur following a tick bite. In North America several species have been implicated, the most common of which is Dermacentor andersoni (Rocky Mountain wood tick), found in the Western and Northwestern USA. In the Eastern USA, Dermacentor variabilis (American dog tick) is the most common culprit [34]. Salivary neurotoxins secreted during tick feeding impact presynaptic acetylcholine release [35, 36], classically causing the onset of an ataxic gait followed by an acute ascending flaccid paralysis within a few 362
Pediatr Neurosurg 2013;49:360–364 DOI: 10.1159/000368278
days of tick attachment. As with some other types of ascending motor dysfunction, tick paralysis is associated with a relative sparing of sensation [6]. Without removal of the inciting parasite, neurological dysfunction can rapidly progress to involve the upper extremities and cranial nerves, and lead to respiratory failure and death [6]. Treatment relies upon the timely diagnosis and removal of the tick. In a recent meta-analysis of tick paralysis in Foster/Zwagerman/Ricks/Greene
the USA, complete neurological recovery averaged 1.4 days after tick removal; in this series, 10% of patients required mechanical ventilation at some point during their clinical course [5]. The last recorded death from tick paralysis occurred in 1979 [37]. Without identification of an inciting tick, the diagnosis is difficult and misdiagnosis common. Patients with ascending paralysis can be thought to have Guillain-Barré syndrome, transverse myelitis, paralytic hysteria, myasthenia gravis (typically in older patients) or spinal cord abnormalities, such as tumors, cysts, vascular abnormalities or ischemia [3, 5]. Clinically, the weakness may be preceded by up to 24 h of vague symptoms of restlessness, fatigue and myalgias [2]. Unlike with other tick-borne illnesses, fever and a classic rash are usually not seen [38]. In our patient there was no reported prodrome, even upon retrospective questioning. Laboratory values, including both serum and cerebrospinal fluid analyses, are typically normal [39]. Nerve conduction studies may aid in the diagnosis, showing a diminished amplitude of compound muscle action potentials with prolonged distal motor nerve latencies but normal sensory potentials [6]. Spinal arachnoid cysts are rarely symptomatic, although symptoms and the secondary need for operative decompression are well reported in the literature [26,
40]. Rapidly progressive myelopathy and radiculopathy have been reported, often from a minor trauma triggering a clinical decompensation [8, 11, 29, 41]. Spinal arachnoid cysts can be seen in association with syringomyelia, as in this case, likely from impairment of normal cerebrospinal fluid flow dynamics. Both the cyst and the syrinx are reported to respond well to surgical decompression and demonstrate resolution on interval imaging [32]. The clinical course of the patient presented in this report was complicated by two rare disease processes. Possibly, the diagnosis of tick paralysis could have been made earlier without the coexistence of a compressive thoracic arachnoid cyst and syrinx. With the clinical decline of the child following uncomplicated surgery, an alternative diagnosis was sought. To our knowledge, this is the first case reported in the literature with concomitant tick paralysis and a symptomatic thoracic arachnoid cyst. Tick paralysis must be included in the differential diagnosis of progressive ascending paralysis in children. Disclosure Statement The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
References 1 Pecina CA: Tick paralysis. Semin Neurol 2012;32:531–532. 2 Rose I: A review of tick paralysis. Can Med Assoc J 1954;70:175–176. 3 Edlow JA, McGillicuddy DC: Tick paralysis. Infect Dis Clin North Am 2008; 22: 397–413, vii. 4 Felz MW, Durden LA: Attachment sites of four tick species (Acari: Ixodidae) parasitizing humans in Georgia and South Carolina. J Med Entomol 1999;36:361–364. 5 Diaz JH: A 60-year meta-analysis of tick paralysis in the United States: a predictable, preventable, and often misdiagnosed poisoning. J Med Toxicol 2010;6:15–21. 6 Grattan-Smith PJ, Morris JG, Johnston HM, Yiannikas C, Malik R, Russell R, Ouvrier RA: Clinical and neurophysiological features of tick paralysis. Brain 1997;120:1975–1987. 7 Needham GR: Evaluation of five popular methods for tick removal. Pediatrics 1985;75: 997–1002. 8 Sharma A, Karande S, Sayal P, Ranadive N, Dwivedi N: Spinal intramedullary arachnoid cyst in a 4-year-old girl: a rare cause of treatable acute quadriparesis: case report. J Neurosurg 2005;102(suppl):403–406.
Thoracic Arachnoid Cyst and Tick Paralysis
9 Weber F, Knopf H: Incidental findings in magnetic resonance imaging of the brains of healthy young men. J Neurol Sci 2006; 240: 81–84. 10 Al-Holou WN, Yew AY, Boomsaad ZE, Garton HJ, Muraszko KM, Maher CO: Prevalence and natural history of arachnoid cysts in children. J Neurosurg Pediatr 2010;5:578– 585. 11 Lee HJ, Cho DY: Symptomatic spinal intradural arachnoid cysts in the pediatric age group: description of three new cases and review of the literature. Pediatr Neurosurg 2001; 35: 181–187. 12 Cloward RB: Congenital spinal extradural cysts: case report with review of literature. Ann Surg 1968;168:851–864. 13 Kumar K, Malik S, Schulte PA: Symptomatic spinal arachnoid cysts: report of two cases with review of the literature. Spine (Phila Pa 1976) 2003;28:E25–E29. 14 Perret G, Green D, Keller J: Diagnosis and treatment of intradural arachnoid cysts of the thoracic spine. Radiology 1962;79:425–429. 15 Agnoli AL, Schonmayr R, Laun A: Intraspinal arachnoid cysts. Acta Neurochir (Wien) 1982; 61:291–302.
16 Lesoin F, Rousseau M, Thomas CE 3rd, Jomin M: Post traumatic spinal arachnoid cysts. Acta Neurochir (Wien) 1984;70:227–234. 17 Cloward RB: Spinal extradural cysts. Ann Surg 1937;105:401–407. 18 McCrum C, Williams B: Spinal extradural arachnoid pouches. Report of two cases. J Neurosurg 1982;57:849–852. 19 Nabors MW, Pait TG, Byrd EB, Karim NO, Davis DO, Kobrine AI, Rizzoli HV: Updated assessment and current classification of spinal meningeal cysts. J Neurosurg 1988; 68: 366– 377. 20 Puijlaert JB, Vielvoye GJ, van Dulken H: Two spinal arachnoid cysts. Case reports and short review of literature. Eur J Radiol 1985;5:135– 138. 21 Uemura K, Yoshizawa T, Matsumura A, Asakawa H, Nakamagoe K, Nose T: Spinal extradural meningeal cyst. Case report. J Neurosurg 1996;85:354–356. 22 Rohrer DC, Burchiel KJ, Gruber DP: Intraspinal extradural meningeal cyst demonstrating ball-valve mechanism of formation. Case report. J Neurosurg 1993;78:122–125. 23 Gortvai P, el-Gindi S: Spinal extradural cyst. Case report. J Neurosurg 1967;26:432–435.
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24 Lake PA, Minckler J, Scanlan RL: Spinal epidural cyst: theories of pathogenesis. Case report. J Neurosurg 1974;40:774–778. 25 Catala M, Poirier J: Arachnoid cysts: histologic, embryologic and physiopathologic review (in French). Rev Neurol (Paris) 1998; 154: 489–501. 26 Bond AE, Zada G, Bowen I, McComb JG, Krieger MD: Spinal arachnoid cysts in the pediatric population: report of 31 cases and a review of the literature. J Neurosurg Pediatr 2012;9:432–441. 27 Fortuna A, La Torre E, Ciappetta P: Arachnoid diverticula: a unitary approach to spinal cysts communicating with the subarachnoid space. Acta Neurochir (Wien) 1977; 39: 259– 268. 28 Goyal RN, Russell NA, Benoit BG, Belanger JM: Intraspinal cysts: a classification and literature review. Spine (Phila Pa 1976) 1987;12: 209–213. 29 Marbacher S, Barth A, Arnold M, Seiler RW: Multiple spinal extradural meningeal cysts presenting as acute paraplegia. Case report and review of the literature. J Neurosurg Spine 2007;6:465–472.
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30 Takeuchi A, Miyamoto K, Sugiyama S, Saitou M, Hosoe H, Shimizu K: Spinal arachnoid cysts associated with syringomyelia: report of two cases and a review of the literature. J Spinal Disord Tech 2003;16:207–211. 31 Andrews BT, Weinstein PR, Rosenblum ML, Barbaro NM: Intradural arachnoid cysts of the spinal canal associated with intramedullary cysts. J Neurosurg 1988;68:544–549. 32 Holly LT, Batzdorf U: Syringomyelia associated with intradural arachnoid cysts. J Neurosurg Spine 2006;5:111–116. 33 Su DK, Ebenezer S, Avellino AM: Symptomatic spinal cord compression from an intradural arachnoid cyst with associated syrinx in a child: case report. Pediatr Neurosurg 2012;48: 236–239.
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34 Vedanarayanan V, Sorey WH, Subramony SH: Tick paralysis. Semin Neurol 2004; 24: 181–184. 35 Cooper BJ, Spence I: Temperature-dependent inhibition of evoked acetylcholine release in tick paralysis. Nature 1976;263:693–695. 36 Emmons P, McLennan H: Failure of acetylcholine release in tick paralysis. Nature 1959; 183:474–475. 37 Zanga JR: Tick paralysis: another lethal tickborne disease. Va Med 1979;106:443–444. 38 Diaz JH: Tick paralysis in the United States. J La State Med Soc 2010;162:273–280. 39 Dworkin MS, Shoemaker PC, Anderson DE: Tick paralysis: 33 human cases in Washington State, 1946–1996. Clin Infect Dis 1999; 29: 1435–1439. 40 Evangelou P, Meixensberger J, Bernhard M, Hirsch W, Kiess W, Merkenschlager A, Nestler U, Preuss M: Operative management of idiopathic spinal intradural arachnoid cysts in children: a systematic review. Childs Nerv Syst 2013;29:657–664. 41 Muthukumar N: Anterior cervical arachnoid cyst presenting with traumatic quadriplegia. Childs Nerv Syst 2004;20:757–760.
Foster/Zwagerman/Ricks/Greene
Copyright: S. Karger AG, Basel 2015. Reproduced with the permission of S. Karger AG, Basel. Further reproduction or distribution (electronic or otherwise) is prohibited without permission from the copyright holder.
Received: April 25, 2014 Accepted after revision: September 7, 2014 Published online: December 17, 2014
Symptomatic Thoracic Arachnoid Cyst with Coexisting Tick Paralysis: Case Report and Review of the Literature Kimberly A. Foster Nathan T. Zwagerman Christian Ricks Stephanie Greene Department of Neurosurgery, Children’s Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, Pa., USA
Established Facts • Tick paralysis is a rare condition which can cause significant morbidity and even death. • Spinal arachnoid cysts are also a rare cause of progressive paralysis.
Novel Insights • Patients can present with multiple underlying etiologies to progressive paralysis. • Tick paralysis must be included in the differential diagnosis of progressive ascending paralysis in children.
Key Words Arachnoid cyst · Thoracic spine · Tick paralysis
Abstract Tick paralysis is an uncommon phenomenon resulting from the release of a neurotoxin from the salivary glands of an engorged, gravid female tick about 5–7 days after attachment. The neurotoxin produces ascending weakness, mimicking other ascending paralytic processes. We present a case of a child presenting with weakness of the lower extremities and frequent falls who was found to have a compressive thoracic arachnoid cyst and a large distal syrinx. After surgical decompression, the patient made significant improvement in
© 2014 S. Karger AG, Basel 1016–2291/14/0496–0360$39.50/0 E-Mail [email protected] www.karger.com/pne
her leg strength, but quickly developed an ascending quadriparesis, followed by respiratory depression. Subsequent imaging and physical examination revealed an engorged tick embedded in her scalp. The tick was removed, and the patient made a rapid and complete clinical recovery. We present a unique case of concomitant tick paralysis and a symptomatic spinal intradural arachnoid cyst, and review the literature on tick paralysis. © 2014 S. Karger AG, Basel
Kimberly A. Foster and Nathan T. Zwagerman shared first authorship of the manuscript.
Kimberly A. Foster, MD Department of Neurosurgery, University of Pittsburgh 4th Floor Faculty Pavilion, 4401 Penn Ave. Pittsburgh, PA 15224 (USA) E-Mail fosterka @ upmc.edu
Tick paralysis is a rare condition which, when overlooked or misdiagnosed, can cause significant morbidity and even death [1]. Most cases occur during the spring or summer months in children younger than 8 years of age [2, 3]. Tick paralysis is more common in girls, possibly due to the length of their hair masking the presence of a tick [4]. The rapidly progressive ascending paralysis is difficult to distinguish from other ascending paralytic diseases such as Guillain-Barré syndrome and poliomyelitis [5]. Treatment primarily consists of removing the tick from the patient, which produces resolution of symptoms in short order [6, 7]. If the tick is not removed, the disease may progress to respiratory arrest and death. Tick paralysis should be considered in any child who has developed a progressive ascending paralysis [3, 5]. Spinal arachnoid cysts are also a rare cause of progressive paralysis [8]. While intracranial arachnoid cysts are identified in 1.7–2.6% of pediatric patients who undergo cranial imaging [9, 10], spinal arachnoid cysts are much less common. These cysts are frequently extradural, dorsal to the spinal cord, and located in the thoracic region [11–13]. They may be congenital (possibly secondary to a widening of the septum posticum [14]) or acquired from inflammation following surgery, meningitis or trauma [15, 16]. Multiple theories regarding the etiology of arachnoid cysts, as well as the impetus for their enlargement over time, have been put forth. A ball valve effect [17–22], the movement of fluid from the subarachnoid space into the cyst due to an osmotic gradient [15, 23, 24] and active secretion from cells lining the cyst [23, 25] have been postulated as mechanisms for cyst enlargement over time. Patients with spinal arachnoid cysts present with back pain and signs of progressive myelopathy, including lower extremity weakness, gait instability, sensory loss, and bowel and bladder dysfunction [16, 26–29]. The association of a syrinx with an intradural arachnoid cyst has been reported in adults [30–32] but was recently reported for the first time in a child [33]. Although both tick paralysis and spinal arachnoid cysts have been cited independently as causes of paralysis in children, this is the first case to our knowledge in which their simultaneous presentation has been reported in the literature.
Case Report
a
b
Fig. 1. MRI of thoracic spine, sagittal images. a Preoperative imaging indicates a dorsal thoracic arachnoid cyst with associated syringomyelia. b Imaging obtained on postoperative day 2 indicates diminished size of both the arachnoid cyst and syringomyelia.
ing and reported that her legs felt ‘wobbly’. In the emergency department, she had the ability to stand with assistance, but refused to stand without assistance. She and her caretaker denied numbness, tingling, or bowel or bladder dysfunction, and reported no recent illness or sick contacts. While tick-borne illnesses are endemic to the region where the child lives, later questioning revealed that she had not recently been outdoors in a known tick-infested area. Her review of systems was unremarkable for fever, rash or other signs of systemic illness. She had no medical or surgical history, was taking no daily medications, and had no known medical or environmental allergies. Complicating her presentation was the fact that she had been with this foster family for only 2 weeks, and there was minimal information regarding her family history. Examination On examination in the emergency department, she was awake, alert and oriented. Her cranial nerves were intact. Upper extremity examination revealed 5/5 strength in all muscle groups, while her lower extremities were 3/5 strength in all muscle groups symmetrically. Sensation was diminished to light touch, proprioception, pain and temperature throughout. Deep tendon reflexes were 2+ in the bilateral upper extremities and 1+ at the patellar and Achilles’ tendons bilaterally. She did not demonstrate ankle clonus or an abnormal plantar response. She was able to bear weight and stand with assistance, though she was unable to stand independently. A 3-tesla MRI with and without the administration of gadolinium was performed through the thoracic and lumbar spine. This indicated a thoracic syrinx extending from T4 to T8, with the greatest diameter measuring 4.5 mm. Dorsal to the C7–T4 levels, an arachnoid cyst was identified to be producing ventral displacement of the cord (fig. 1).
History A 4-year-old female child presented to the emergency department of a large pediatric tertiary care center in May with the onset of progressive lower extremity weakness over the preceding 2 days. She awoke on the day prior to her presentation with difficulty walk-
Operation The patient underwent a T2–T4 laminectomy, midline durotomy and wide fenestration of the arachnoid cyst into the normal surrounding subarachnoid space. The cyst was noted to be under high pressure; the arachnoid membrane of the cyst was found to
Thoracic Arachnoid Cyst and Tick Paralysis
Pediatr Neurosurg 2013;49:360–364 DOI: 10.1159/000368278
361
Color version available online
be opaque and thickened, in contrast to the normal wispy arachnoid. The spinal cord was visualized to be flattened and displaced ventrally. Postoperative Course Postoperatively, the child was extubated in the operating room and documented by the surgical and anesthesia services to be moving her legs spontaneously and symmetrically. On postoperative day 1, the patient developed respiratory distress and required reintubation. At this time, motor strength was full in her arms and 4/5 in her legs. A chest X-ray revealed a pulmonary infiltrate, she was diagnosed with pneumonia, and antibiotic therapy was initiated. Over the ensuing 3 days, the patient failed extubation multiple times. She became gradually weaker during this time, initially in the distal lower extremities and progressing rostrally and her strength deteriorated to 1/5 proximally and 2/5 distally in the bilateral upper extremities, 1/5 in the left lower extremity and 2/5 in the right lower extremity. A repeat MRI including the entire neuraxis indicated near-complete resolution of the arachnoid cyst and syrinx, with expected postoperative changes and no new abnormalities. Due to ongoing paralysis, electromyography and nerve conduction studies were completed. The latter revealed low compound motor action potentials in multiple nerves with preserved sensory nerve action potentials. There was no prolongation in conduction velocity seen, and normal F wave responses were noted, suggesting a diffuse motor axonal neuropathy or a presynaptic neuromuscular junction disturbance. On detailed physical examination of the patient, an engorged tick was noted behind the patient’s left ear and was carefully removed by grasping the tick as closely as possible to its attachment site and using steady traction to ensure the head or mouthparts did not remain engaged, so as to avoid leaving behind neurotoxin still present in the salivary glands. The tick was identified as a gravid female of the Dermacentor species (fig. 2). On further review of the imaging, MRI of the brain revealed an abnormal extracranial mass behind the left ear embedded in the scalp (fig. 3). Within 12 h following tick removal, the child was able to move all extremities against gravity. She had the rapid return of respiratory effort, and was weaned off of the ventilator and extubated approximately 36 h after tick removal. On postoperative day 16, she was discharged to home with outpatient physical therapy. At her initial postoperative visit 3 weeks after surgery, she was neurologically intact and had resumed her baseline activity level.
Fig. 2. Gross pathology specimen of the tick removed from the
child’s scalp, identified as a gravid female Dermacentor variabilis.
Fig. 3. MRI of brain, coronal image. Note identification of an ex-
tracranial lesion found to be an engorged Dermacentor tick, known to produce symptoms of tick paralysis (white arrow).
Discussion
Tick paralysis is a rare entity that can occur following a tick bite. In North America several species have been implicated, the most common of which is Dermacentor andersoni (Rocky Mountain wood tick), found in the Western and Northwestern USA. In the Eastern USA, Dermacentor variabilis (American dog tick) is the most common culprit [34]. Salivary neurotoxins secreted during tick feeding impact presynaptic acetylcholine release [35, 36], classically causing the onset of an ataxic gait followed by an acute ascending flaccid paralysis within a few 362
Pediatr Neurosurg 2013;49:360–364 DOI: 10.1159/000368278
days of tick attachment. As with some other types of ascending motor dysfunction, tick paralysis is associated with a relative sparing of sensation [6]. Without removal of the inciting parasite, neurological dysfunction can rapidly progress to involve the upper extremities and cranial nerves, and lead to respiratory failure and death [6]. Treatment relies upon the timely diagnosis and removal of the tick. In a recent meta-analysis of tick paralysis in Foster/Zwagerman/Ricks/Greene
the USA, complete neurological recovery averaged 1.4 days after tick removal; in this series, 10% of patients required mechanical ventilation at some point during their clinical course [5]. The last recorded death from tick paralysis occurred in 1979 [37]. Without identification of an inciting tick, the diagnosis is difficult and misdiagnosis common. Patients with ascending paralysis can be thought to have Guillain-Barré syndrome, transverse myelitis, paralytic hysteria, myasthenia gravis (typically in older patients) or spinal cord abnormalities, such as tumors, cysts, vascular abnormalities or ischemia [3, 5]. Clinically, the weakness may be preceded by up to 24 h of vague symptoms of restlessness, fatigue and myalgias [2]. Unlike with other tick-borne illnesses, fever and a classic rash are usually not seen [38]. In our patient there was no reported prodrome, even upon retrospective questioning. Laboratory values, including both serum and cerebrospinal fluid analyses, are typically normal [39]. Nerve conduction studies may aid in the diagnosis, showing a diminished amplitude of compound muscle action potentials with prolonged distal motor nerve latencies but normal sensory potentials [6]. Spinal arachnoid cysts are rarely symptomatic, although symptoms and the secondary need for operative decompression are well reported in the literature [26,
40]. Rapidly progressive myelopathy and radiculopathy have been reported, often from a minor trauma triggering a clinical decompensation [8, 11, 29, 41]. Spinal arachnoid cysts can be seen in association with syringomyelia, as in this case, likely from impairment of normal cerebrospinal fluid flow dynamics. Both the cyst and the syrinx are reported to respond well to surgical decompression and demonstrate resolution on interval imaging [32]. The clinical course of the patient presented in this report was complicated by two rare disease processes. Possibly, the diagnosis of tick paralysis could have been made earlier without the coexistence of a compressive thoracic arachnoid cyst and syrinx. With the clinical decline of the child following uncomplicated surgery, an alternative diagnosis was sought. To our knowledge, this is the first case reported in the literature with concomitant tick paralysis and a symptomatic thoracic arachnoid cyst. Tick paralysis must be included in the differential diagnosis of progressive ascending paralysis in children. Disclosure Statement The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
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