Range of motion in the cervical spine after odontoid fracture treated with anterior screw fixation.

BACKGROUND: It is believed that direct odontoid screw fixation preserves the physiological cervical range of motion following surgery. However, there are no clinical studies confirming the motion sparing value of this technique. This study aims to (1) to assess active cervical range of motion following types II and III odontoid fracture, successfully treated with anterior odontoid screw fixation, and (2) to examine the relationship between the range of motion of the head and duration of collar usage, neck pain, quality of life, and patients' age. METHODS: The study involved 41 patients subjected to a procedure of direct osteosynthesis of the dens with lag screw. Following the operation all the patients had to wear a cervical collar to protect the osteosynthesis. The control group consisted of 41 individuals with no clinical diagnosis of any cervical spine disorders. The spinal motion was assessed using multi-cervical unit, taking into account bending/extension, left and right lateral flexion, and left and right axial rotation. RESULTS: In the study group, spine mobility correlated with the duration of hard collar usage following the operation, with a longer duration corresponding to poorer spine mobility at the end of the treatment. Statistically significant correlation was observed in the case of extension (p < 0.021) and axial rotation (p < 0.007). In the study group, there was a negative correlation between the range of motion and the patients' age, i.e., the older the patient the poorer his/her spinal mobility (p < 0.001). CONCLUSIONS: Active cervical range of motion in patients following direct osteosynthesis of the dens, augmented with a hard collar, was significantly lower than in the control population, and it correlated negatively with the duration of collar usage, the patients' age, and intensity of spinal pain.

The Most Influential Publications in Odontoid Fracture Management.

OBJECTIVE: Management of odontoid fractures has improved and evolved due to advancing diagnostic guidelines and understanding of long-term outcomes. The aim of this study was to quantify the most frequently cited publications pertaining to odontoid fractures and determine their validity as a tool to practice evidence-based medicine. METHODS: A Clarivate Analytics Web of Science search was used to identify all articles related to odontoid fractures. The 50 most cited articles were reviewed. Criteria included the frequency of citation, year of publication, countries of origin, journal, levels of evidence (LOE), article types, and supporting authors and institutions. RESULTS: The top 3 most cited papers were "Radiological and anatomical evaluation of the atlantoaxial transarticular screw fixation technique" (Madawi 1997), "Atlantoaxial fixation using, plate and screw method: A report of 160 treated patients" (Goel 2002), and "The anatomical suitability of the C1-2 complex for transarticular screw fixation" (Paramore 1996). Spine (n = 13; 26%) was the most common journal, and the most frequent decade was 2000-2009 (n = 18; 36%). The United States was associated with the greatest number of publications, and the most common article type was clinical outcomes (n = 16; 32%). The most recurring LOE was IV (n = 20; 40%). CONCLUSIONS: This review provides a comprehensive understanding of the historical literature pertaining to odontoid fracture management. There is a paucity of high LOE publications regarding this topic, and clinicians should strive to provide more high-level studies. This article can help practitioners navigate the vast body of literature about this topic and identify high-impact publications.

It is the lateral head tilt, not head rotation, causing an asymmetry of the odontoid-lateral mass interspace.

OBJECTIVE: Asymmetry in odontoid-lateral mass interspace in trauma patients is a common finding that regularly leads to additional diagnostic work-up, since its dignity is not entirely clear. There is little evidence in the literature that atlantoaxial asymmetry is associated with C1-C2 instability or (sub) luxation. Asymmetry in odontoid-lateral mass interspace seems to occur occasionally in healthy individuals and patients suffering a cervical spine injury. Congenital abnormalities in odontoid-lateral mass asymmetry may mimic an atlantoaxial asymmetry. The center of C1-C2 rotation is based in the peg of dens axis; therefore, a C1-C2 rotational influence seems unlikely. So far, no study examined the influence of C0-C1-C2 tilt to an asymmetry in odontoid-lateral mass interspace. SUBJECTS AND METHODS: In order to determine if rotation or tilt influences the lateral atlantodental interval (LADI) and to estimate physiologic values, we examined 300 CT scans of the cervical spine. RESULTS: The mean LADI was 3.57 mm and the mean odontoid-lateral mass asymmetry was 1.0 mm. Head position during CT examination was found to be rotated in 39 % of the cases in more than 5°. Subsequent mean C0/C2 rotation was 4.6°. There was no significant correlation between atlantoaxial asymmetry and head rotation (p = 0.437). The average tilt of C0-C1-C2 was found to be 2°. We found a significant correlation between tilt of C0-C1-C2 and asymmetry in odontoid-lateral mass interspace (p = 0.000). CONCLUSION: We conclude that an atlantoaxial asymmetry revealed in CT scans of the cervical spine occurs occasionally. Since head tilt correlates with an atlantoaxial asymmetry, it is crucial to perform cervical spine CT scans in a precise straight head position.

Intubation Biomechanics: Laryngoscope Force and Cervical Spine Motion during Intubation in Cadavers-Cadavers versus Patients, the Effect of Repeated Intubations, and the Effect of Type II Odontoid Fracture on C1-C2 Motion.

BACKGROUND: The aims of this study are to characterize (1) the cadaver intubation biomechanics, including the effect of repeated intubations, and (2) the relation between intubation force and the motion of an injured cervical segment. METHODS: Fourteen cadavers were serially intubated using force-sensing Macintosh and Airtraq laryngoscopes in random order, with simultaneous cervical spine motion recorded with lateral fluoroscopy. Motion of the C1-C2 segment was measured in the intact and injured state (type II odontoid fracture). Injured C1-C2 motion was proportionately corrected for changes in intubation forces that occurred with repeated intubations. RESULTS: Cadaver intubation biomechanics were comparable with those of patients in all parameters other than C2-C5 extension. In cadavers, intubation force (set 2/set 1 force ratio = 0.61; 95% CI, 0.46 to 0.81; P = 0.002) and Oc-C5 extension (set 2 - set 1 difference = -6.1 degrees; 95% CI, -11.4 to -0.9; P = 0.025) decreased with repeated intubations. In cadavers, C1-C2 extension did not differ (1) between intact and injured states; or (2) in the injured state, between laryngoscopes (with and without force correction). With force correction, in the injured state, C1-C2 subluxation was greater with the Airtraq (mean difference 2.8 mm; 95% CI, 0.7 to 4.9 mm; P = 0.004). CONCLUSIONS: With limitations, cadavers may be clinically relevant models of intubation biomechanics and cervical spine motion. In the setting of a type II odontoid fracture, C1-C2 motion during intubation with either the Macintosh or the Airtraq does not appear to greatly exceed physiologic values or to have a high likelihood of hyperextension or direct cord compression.

Maximal rotation at atlanto-axial joint: analysis of changes in mid-sagittal space within atlas vertebra

The present study was conducted to analyses changes that may occur in the available antero-posterior dimension (behind the dens) within the ring of the atlas vertebra resulting from optimal axial rotation of the neck. Radiographs were at obtained from twentyfive healthy volunteers of both sexes between the age group 25-50 years. The subjects recruited for the study were healthy individuals, with no any history of major ailments of the spine and did not show any unilateral or bilateral restriction of axial rotation at the neck. Outcome measures were evaluated by data obtained with and without axial rotation and were statistically compared for difference in means, their ratios, correlation and dependence. The anterior (AS) as well as the posterior spaces (PS) available respectively in front of and behind the odontoid process reduced in rotation. The reduction at the PS (average .89 mm) was 4.10 % of the available space observed without rotation. Although the reduction at the PS may not compress the spinal cord, extreme axial rotation with flexion may possibly compress the contents of the spinal canal, where atlas rings are smaller or accommodate a space-occupying lesion (AU)

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The transverse occipital ligament: anatomy and potential functional significance.

BACKGROUND: Knowledge of the anatomy of ligaments that bind the craniocervical junction is important for treating patients with lesions of this region. Although the anatomy and function of these ligaments have been well described, those of the transverse occipital ligament (TOL) have remained enigmatic. OBJECTIVE: To describe the anatomy and functions of the transverse occipital ligament. METHODS: Via a posterior approach, 9 cadaveric specimens underwent dissection of the craniocervical junction with special attention to the presence and anatomy of the TOL. RESULTS: The TOL was identified in 77.8% of the specimens. The ligament was found to be rectangular with fibers running horizontally between the lateral aspects of the foramen magnum. The attachment of each ligament near the occipital condyle was consistent, and each ligament was found superior to the transverse portion of the cruciform ligament and inserted just posterior to the lateral attachment sites of the alar ligaments. The average width, length, and thickness of the TOL was 0.34, 1.94, and 0.13 cm, respectively. The TOL in some specimens also had connections to the alar and transverse ligaments. CONCLUSION: The TOL was found in the majority of our specimens. The possible functions of this ligament when attached to the alar ligaments include providing additional support to these structures in stabilizing lateral bending, flexion, and axial rotation of the head. Knowledge of this ligament may aid in further understanding craniocervical stability and help in differentiating normal from pathology via imaging modalities.

Atlantoaxial rotatory fixation.

OBJECTIVE: Atlantoaxial rotatory fixation (AARF) remains a recondite entity. Our normative study using CT motion analysis shows that there is a high degree of concordance for rotational behavior of C1 and C2 in children 0 to 18 years. C1 always crosses C2 at or near 0 degree. The predictable relationship between C1 and C2 is depicted by 3 distinct regions on the motion curve: when C1 rotates from 0 to 23 degrees, it moves alone while C2 remains stationary at 0 (the single-motion phase). When C1 rotates from 24 to 65 degrees, C1 and C2 move together (the double-motion phase), but C1 always moves faster as C2 is being pulled by yoking ligaments. From 65 degrees onward, C1 and C2 move in unison (the unison-motion phase) with a fixed, maximal separation angle of approximately 43 degrees, the head rotation being carried exclusively by the subaxial segments. Because of this high concordance among patients and a relatively narrow variance from the mean, the physiological composite motion curve can be used as a normal template for the diagnosis and classification of AARF. METHODS: Using a 3-position CT protocol to obtain the diagnostic motion curve, we identified 3 distinct types of AARF. Type I AARF patients show essentially unaltered ("locked") C1-C2 coupling regardless of corrective counterrotation, with curves that are horizontal lines in the upper 2 quadrants of the template. Type II AARF patients show reduction of the C1-C2 separation angle with forced correction, but C1 cannot be made to cross C2. Their curves slope downward from the right to left upper quadrants but never traverse the x axis. Type III AARF patients show C1-C2 crossover but only when the head is cranked far to the opposite side. Their motion curves traverse the x axis far left of 0 degree (C1 < -20). Thus, type I, II, and III AARF are in descending degrees of pathological stickiness. A fourth group of patients showing motion curve features between normal and type III AARF are designated as belonging to a diagnostic gray zone (DGZ). The AARF patients are further classified as acute if treatment is started less than 1 month from the onset of symptoms, as subacute if the delay in treatment is 1 to 3 months, and chronic if treatment delay exceeds 3 months. The treatment protocol for AARF consists of reduction using either halter or caliper traction and then immobilization with brace or halo, depending on the AARF type and chronicity. Recurrent slippage and irreducibility are treated with C1-C2 fusion. RESULTS: The treatment course and outcome of AARF are analyzed according to the AARF type and chronicity. The difficulty and duration of treatment, the number of recurrent slippage, the rate of irreducibility, the need for halo and fusion, and the percentage ultimately losing normal C1-C2 rotation are significantly greater in type I patients than type III patients, with type II patients somewhere in between. Likewise, all parameters are much worse in patients with any type of chronic AARF than acute AARF. The worse subgroup is chronic type I versus the best subgroup of acute type III. Recurrent AARF patients do much worse than nonrecurrent AARF patients. Recurrence is, in turn, adversely influenced by both the severity (type) and chronicity of AARF. The symptoms of most DGZ patients will resolve with analgesics, but a few remain symptomatic or deteriorate to true AARF requiring the full treatment. CONCLUSION: Thus, children with painful torticollis should undergo the 3-position CT protocol not only to confirm the diagnosis of AARF but also to grade its severity. Closed reduction with traction should be instituted immediately to avoid the serious consequences of chronicity. Proper typing and reckoning of the pretreatment delay are requisites for selecting treatment modalities. Recurrent dislocation and incomplete reduction should be treated with posterior C1-C2 fusion in the best achievable alignment.

Biomechanics of halo-vest and dens screw fixation for type II odontoid fracture.

STUDY DESIGN: An in vitro biomechanical study of halo-vest and odontoid screw fixation of Type II dens fracture. OBJECTIVE: The objective were to determine upper cervical spine instability due to simulated dens fracture and investigate stability provided by the halo-vest and odontoid screw, applied individually and combined. SUMMARY OF BACKGROUND DATA: Previous studies have evaluated posterior fixation techniques for stabilizing dens fracture. No previous biomechanical study has investigated the halo-vest and odontoid screw for stabilizing dens fracture. METHODS: A biofidelic skull-neck-thorax model was used with 5 osteoligamentous whole cervical spine specimens. Three-dimensional flexibility tests were performed on the specimens while intact, following simulated dens fracture, and following application of the halo-vest alone, odontoid screw alone, and halo-vest and screw combined. Average total neutral zone and total ranges of motion at C0/1 and C1/2 were computed for each experimental condition and statistically compared with physiologic motion limits, obtained from the intact flexibility test. Significance was set at P < 0.05 with a trend toward significance at P < 0.1. RESULTS: Type II dens fracture caused trends toward increased sagittal neutral zone and lateral bending range of motion at C1/2. Spinal motions with the dens screw alone could not be differentiated from physiologic limits. Significant reductions in motion were observed at C0/1 and C1/2 in flexion-extension and axial rotation due to the halo-vest, applied individually or combined with the dens screw. At C1/2, the halo-vest combined with the dens screw generally allowed the smallest average percentages of intact motion: 3% in axial rotation, 17% in flexion-extension, and 18% in lateral bending. CONCLUSION: The present reduction in C1/2 motion observed, due to the halo-vest and dens screw combined is similar to previously reported immobilization provided by the polyaxial screw/rod system and transarticular screw fixation combined with wiring. The present biomechanical data may be useful to clinicians when choosing an appropriate treatment for those with Type II dens fracture.

Artificial atlanto-odontoid joint replacement through a transoral approach.

Resection of the odontoid process and anterior arch of the atlas results in atlantoaxial instability, which if left uncorrected may lead to severe neurological complications. Currently, such atlantoaxial instability is corrected by anterior and/or posterior C1-C2 fusion. However, this results in considerable loss of rotation function of the atlantoaxial complex. From the viewpoint of retaining the rotation function and providing stability, we designed an artificial atlanto-odontoid joint based on anatomical measurements of 50 pairs of dry atlantoaxial specimens by digital calipers and 10 fresh cadaveric specimens by microsurgical techniques. The metal-on-metal titanium alloy joint has an arc-shaped atlas component, and a hollow cylindrical bushing into which fits a rotation axle of an inverted v-shaped axis component and is implanted through a transoral approach. After the joint was implanted onto specimens with anterior decompression, biomechanical tests were performed to compare the stability parameters in the intact state, after decompression, after artificial joint replacement, and after fatigue test. Compared to the intact state, artificial joint replacement resulted in a significant decrease in the range of motion (ROM) and neutral zone (NZ) during flexion, extension, and lateral bending (P < 0.001); however, with regard to axial rotation, there was no significant difference in ROM (P = 0.405), a significant increase in NZ (P = 0.008), and a significant decrease in stiffness (P = 0.003). Compared to the decompressed state, artificial joint replacement resulted in a significantly decreased ROM (P B 0.021) and NZ (P B 0.002) and a significantly increased stiffness (P \ 0.001) in all directions. Following artificial joint replacement, there was no significant difference in ROM (P C 0.719), NZ (P C 0.580), and stiffness (P C 0.602) in all directions before and after the fatigue test. The artificial joint showed no signs of wear and tear after the fatigue test. This artificial atlanto-odontoid joint may be useful in cases of odontoid resection due to malunion or nonunion of odontoid fracture, atraumatic odontoid fracture, irreducible atlas dislocation, posterior atlantoaxial subluxation, or congenital skull base abnormalities.

Clinical implications of alignment of upper and lower cervical spine.

AIMS AND OBJECTIVES: The alignment of upper and lower cervical spine is presumed to be closely interrelated and the knowledge of this is mandatory when performing occipito-cervical and upper cervical fusions. The aim of this study was to establish standard values for upper and lower cervical spine alignment in the Indian population. MATERIALS AND METHODS: Five hundred eighteen asymptomatic volunteers (261 males and 257 females) between 12 and 80 years of age underwent lateral radiography with their neck in the neutral position. Angles for occipital to 2nd cervical (Oc-C2), 1st to 2nd cervical (C1-C2) and sagittal alignment of 2nd to 7th cervical vertebrae (C2-C7) were measured. Statistical analyses were performed using a statistical package SPSS 10 for windows and the students 't' test. RESULTS: The mean Oc-C2, C1-C2 and C2--C7 angles were 14.66+9.5 degrees , 25.6+7.9 degrees and 16.8+12.7 degrees in male, while same angles in female were 15.59+8.26 degrees, 26.9+6.8 degrees and 9.11+10.4 degrees respectively. Weak statistically significant negative correlation was observed between the measured angles of the upper (Oc-C2 and C1-C2) and lower (C2-C7) cervical spines, which means if the lordosis of the occiput and upper cervical spine increases (if the Oc-C2 angle increases), the alignment of lower cervical spine becomes kyphotic and vice versa. This negative correlation was stronger between the Oc-C2 and C2-C7 angles than between the C1-C2 and C2-C7 angles. CONCLUSIONS: Relationship between alignment of the upper and the lower cervical spine should be taken into consideration when performing cervical fusion.

Anterior screw fixation for a pediatric odontoid nonunion: a case report.

STUDY DESIGN: A case of an odontoid nonunion in a child treated with anterior screw fixation. OBJECTIVES: To demonstrate that an anterior screw procedure can be performed with an odontoid nonunion with resultant fusion to maintain range of motion. METHODS: A 15-year-old boy presented with pain in his neck following a rugby football injury. Admission plain radiographs and computed tomography scan demonstrated an odontoid nonunion. Radiographs of a previous cervical spine injury 2 years before demonstrated a missed odontoid fracture. RESULTS: The child was initially treated conservatively with halo vest immobilization, which did not result in healing. Direct anterior screw fixation was performed and the fracture united 5 months following surgery. DISCUSSION: The nonunion was asymptomatic for 2 years until the second injury when it became clinically symptomatic. It did not respond to conservative treatment and was unstable on screening requiring operative intervention. CONCLUSIONS: Very few cases have been reported of pediatric odontoid nonunions. If the fracture pattern allows, then direct anterior screw fixation should be considered in order to maintain range of motion at the atlantoaxial articulation.

Stresses on the cervical column associated with vertical occlusal alteration.

The biomechanical effects on cervical vertebral columns (C1-C7) during mastication were calculated using a three-dimensional (3D) finite element method. To verify the biomechanical influences of vertical occlusal alteration to the cervical column, three finite element models (FEM) showing a normal (model A), a steep (model B), and a flat occlusal plane (model C) were constructed. The occlusal stress distribution showed various patterns for the three models; the stress extended to the anterior area as the occlusal plane became steeper. The plots of the stresses on the mid sagittal section of the cervical columns showed different patterns for the three models; the stress converged at the odontoid process in models A and B, whereas the stresses at C7 in model B tended to decrease compared with model A. Concentrated stress was observed at C5 in model C, supporting the hypothesis that vertical occlusal alteration could influence stress distribution in the cervical columns.

Biomechanical testing of posterior atlantoaxial fixation techniques.

STUDY DESIGN: An in vitro biomechanical study of C1-C2 posterior fusion techniques was conducted using a cadaveric model. OBJECTIVE: To investigate and compare the acute stability afforded by a novel rod-based construct that uses direct polyaxial screw fixation to C1 and C2 with contemporary transarticular screw and wire techniques. SUMMARY AND BACKGROUND DATA: Acute stability of the atlantoaxial complex is required to achieve bony consolidation. Various forms of posterior wiring were the first standardized procedures advocated to achieve C1-C2 fixation, but because of insufficient construct stability, these techniques have been coupled with transarticular screw fixation. Significant technical difficulties, however, including the possibility of neurovascular compromise during implantation are associated with transarticular screw placement. A novel technique that uses direct polyaxial screw fixation to C1 and C2 and bilateral longitudinal rods was developed recently. However, there are no published reports detailing the biomechanical characteristics of this new construct. METHODS: In this study, 10 fresh-frozen human cadaveric cervical spines with occiput (C0-C4) were used. Osteoligamentous specimens were tested in their intact condition after destabilization via odontoidectomy, and after two different Gallie wiring techniques. Each specimen was assigned to one of the two screw fixation groups. Five specimens were implanted with the polyaxial screw-rod construct and tested. The remaining five specimens were tested after application of bilateral C1-C2 transarticular screws with Gallie wiring (Magerl-Gallie technique). Pure-moment loading, up to 1.5 Nm in flexion and extension, right and left lateral bending and right and left axial rotation, was applied to the occiput, and relative intervertebral rotations were determined using stereophotogrammetry (motion analysis system). Range of motion data for all fixation scenarios were normalized to the destabilized case, and statistical analysis was performed using one-way analysis of variance with Fisher's least significant difference PLSD post hoc test for multiple comparisons. RESULTS: The data indicate that destabilization via odontoidectomy significantly increased C1-C2 motion. Both screw techniques significantly decreased motion, as compared with both Gallie wiring methods in lateral bending and axial rotation (P < 0.02 for all) and tended toward reduced motion in flexion-extension. There was no statistically significant difference between the two screw techniques. CONCLUSIONS: The results clearly indicate the screw-rod system's equivalence in reducing relative atlantoaxial motion in a severely destabilized upper cervical spine, as compared with the transarticular screw-wiring construct. These findings mirror the previously reported clinical results attained using this new screw-rod construct. Thus, the decision to use either screw construct should be based on safety considerations rather than acute stability.

Safety of neck rotation for ear surgery in children with Down syndrome.

OBJECTIVE: Seek information about spinal cord safety for children with Down syndrome positioned for ear surgery. STUDY DESIGN: Prospective consecutive patients, each serving as his or her own control. METHODS: Somatosensory evoked potentials were recorded from 17 children who were undergoing elective otolaryngological surgery. None of the patients had neurological symptoms or physical examination findings suggesting cervical spinal cord embarrassment. Specifically, muscle tone was normal or mildly reduced globally, consistent with Down syndrome, and deep tendon reflexes were normal and not appreciably different in the upper and lower extremities. On plain lateral radiographs obtained in the neutral, flexed, and extended positions, the patients' cervical spines were normal. RESULTS: When the anesthetized children had their necks placed in either right or left 60 degrees rotation, no significant change in somatosensory latency or amplitude was found. With more than 99.999% certainty, neurologically intact children with Down syndrome with normal plain cervical spine radiographs were not exposed to extra risks by 60 degrees neck rotation during surgery. CONCLUSION: Patients with Down syndrome who are neurologically intact and who have normal lateral neck radiographs do not appear at great risk with neck rotation.

The apical ligament: anatomy and functional significance.

OBJECT: The authors conducted a study to describe the detailed anatomy of the apical ligament and to acknowledge or refute its historical description as a functionally significant contributor to craniocervical stability. METHODS: In 20 adult human cadavers measurements of the apical ligament were obtained, and its detailed anatomy was observed. Ranges of motion were also assessed to discern the function of the apical ligament. CONCLUSIONS: Results of the study support the concept that the apical ligament is best described as a vestigial structure that offers no significant added stability to the craniocervical junction. In fact, this ligament was absent in 20% of the specimens examined. These data will aid physicians who frequently view images or manage clinical problems of the craniocervical junction because they may focus on other ligaments of this area and not the apical ligament.

A biomechanical study of odontoid fractures and fracture fixation.

The purpose of this study was to measure the stability of the odontoid process after fracture and subsequent screw fixation. To accomplish this, we mechanically reproduced Type II and Type III odontoid fractures on isolated C2 vertebrae by varying the direction of load. These fractures were subsequently stabilized with a single 3.5 mm screw and retested for multidirectional stability and load to failure. Reduced and instrumented specimens were found to have a stiffness equivalent to one half of that of the unfractured odontoid. Load to failure was also slightly less than one half of the original fracture force (average 160 lb). Screw failure was by a cut-out mechanism in all Type III fractures and by bending of the screw in all Type III fractures. Our findings, in conjunction with the existing literature, strongly suggest that Type III fractures result from extension forces, whereas Type II fractures result from lateral or oblique loading forces. Single screw fixation of an odontoid fracture will provide stability equal to approximately one half that of the unfractured bone.

Natural history of os odontoideum.

Os odontoideum has recently been considered an acquired lesion of the second cervical vertebrae. This case documents the natural progression of the formation of os odontoideum and correlates it with a traumatic event. This is the first case reported in the literature.