Longus Colli Research Articles

Retropharyngeal Calcific Tendonitis: Report of Two Cases

Retropharyngeal calcific tendonitis is an inflammatory process of the superior oblique tendons of the longus colli muscle, a neck flexor in the upper cervical spine, caused by deposition of calcium hydroxyapatite crystals; the definitive diagnostic test is computed tomography (CT). Presented in this article are two cases seen at our institution. Patients typically present with acute onset of neck pain/spasm, odynophagia, dysphagia, and/or low grade fevers. Leukocytosis and elevated erythrocyte sedimentation rate may be noted. It is important to understand this entity because its signs and symptoms are mimickers of those of the more serious condition of retropharyngeal space abscess. Calcific tendonitis is managed conservatively whereas retropharyngeal abscess requires incision and drainage. Some may argue that this entity is a zebra because its reported incidence in the literature is low. However, most of these studies were done in an era when CT was not yet in vogue. With today's widespread use of CT and its superb ability to visualize the calcification, the true incidence of this condition is probably higher and, thus, it is important for the family practitioner to be aware of this entity. The astute clinician may save the patient from unnecessary diagnostic workup, undue anxiety, and delays in hospital discharge.

Response to reply to the letter to the editor concerning “Gebauer et al.: Subdental synchondrosis and anatomy of the axis in aging: a histomorphometric study on 30 autopsy cases. Eur Spine J 15(3):292–298, 2006”: The basis of the dens axis. Where is it located?

Response to reply to the letter to the editor concerning “Gebauer et al.: Subdental synchondrosis and anatomy of the axis in aging: a histomorphometric study on 30 autopsy cases. Eur Spine J 15(3):292–298, 2006”: The basis of the dens axis. Where is it located?

The terminal insertional segments and communications of the vertebral nerve in the human cervical region

Twenty-four cadavers (48 sides) were used to clarify the terminal insertional segment and communications of the vertebral nerve in the cervical region under a surgical microscope. After displacing the prevertebral muscles (longus colli and longus capitis) laterally, the ventral parts of the transverse foramen of vertebrae (from C2 to C6) were removed, and the insertional segment and communicates of the vertebral nerve surrounding the vertebral artery were observed. The results showed: (1) the vertebral nerve ascended along the ventral or mediodorsal vertebral artery and terminated mainly at C3 (22/36 sides) but not terminated at C4 or C5 only; (2) the superficial communicates from the cervical sympathetic trunk ran in a proximal and distal direction when the fibers entered the anterior branches of the cervical nerves. The fibers running to the proximal direction communicated with the vertebral nerve in the part of transverse foramen; (3) motor and/or sensory rami supplying the prevertebral muscles, corpus vertebrae and intervertebral discs could pass through an "arched-shaped" fiber bundle on the ventral surface of the vertebral artery. In conclusion, the vertebral nerve and the fibers surrounding the vertebral artery could be considered as a stable deep pathway of cervical sympathetic nerves. The deep pathway (vertebral nerve and its branches) with the superficial pathways (cervical sympathetic trunk and its branches) formed a sympathetic nervous "plexus" in the cervical region. This sympathetic nervous "plexus" may be involved in the effects of cervical ganglionic blockade.

Anatomical Variations of the Vertebral Artery Segment in the Lower Cervical Spine

Observational study with retrospective computerized tomography (CT) angiography analysis. The purpose of this study is to examine the vertebral artery's course in the V2 segment and define the anatomic variations in the adult population using CT angiography. The V2 segment of the vertebral artery (VA) usually extends from the transverse processes of C6-C2; however, the presence of abnormal VA course has been reported. These variations may predispose a patient to higher risk of iatrogenic vascular injury during anterior cervical surgery. Retrospectively, 700 vertebral arteries on 350 three-dimensional CT angiographies were analyzed. Measurements were taken describing the relationship between the extraosseous portions of the VA to surgical landmarks. In addition, the diameter of the transverse foramen was measured on axial CT images. The VA entered the C6 transverse process in 94.9% of the specimens (664 out of 700 VA courses). Abnormal VA entrance was observed in 5.1% of the specimens (36 VA courses), with entrance into the C4, C5, or C7 transverse foramen 1.6%, 3.3%, and 0.3%, respectively.In 2 of 36 cases (5.6%) of abnormal VA entrance, the extraosseous VA formed an unusual medial loop, and the center of VA was positioned medial to the longus colli muscle. Furthermore, transverse foramens filled with VA were significantly larger than unfilled foramens (P < 0.01), but there was no significant difference between the C7 unfilled foraminal area and unfilled foraminal area above C7 (P = 0.768). The present study confirms the presence of anomalous VA routes in the V2 segment. A preoperativethree-dimensional computerized tomography (CT) angiography with axial images may be useful to identify the presence of an anomalous V2 route when suspected on magnetic resonance imaging or CT. Delineation of this anomaly may reduce the risk of intraoperative VA injury.

Validity and reliability of ultrasonography for the longus colli in asymptomatic subjects

The purposes of this study were to evaluate the reliability and validity of ultrasound (US) for measuring the cross-sectional area (CSA) of the longus colli (LC) as compared with magnetic resonance imaging (MRI), and to determine the change in CSA of the LC during contraction. 27 healthy volunteers participated in the study. In order to assess the validity of US, the US measurements of the CSA of the LC were compared to those determined with MRI. Two testers established the measurements to ascertain intra- and interrater reliability. The widely spaced limits of agreement (2SD = ±0.45) reflect the large variability between the measurements by US and MRI. The ICC for the intra- and interrater reliability for the CSA of the LC was respectively 0.71 (95% CI, 0.57–0.81; SEM, 0.17; SDD, 0.48) and 0.68 (95% CI, 0.48–0.81; SEM, 0.18; SDD, 0.50). The CSA of the LC increased significantly during contraction of the LC ( p = 0.006). Results from this study show that the validity and reliability of US to evaluate the CSA of the LC is questionable, which may be due to both anatomical characteristics and methodological limitations.

Surgical anatomy of the cervical sympathetic trunk during anterolateral approach to cervical spine

The sympathetic trunk is sometimes damaged during the anterior and anterolateral approach to the cervical spine, resulting in Horner's syndrome. No quantitative regional anatomy in fresh human cadavers describing the course and location of the cervical sympathetic trunk (CST) and its relation to the longus colli muscle (LCM) is available in the literature. The aims of this study are to clearly delineate the surgical anatomy and the anatomical variations of CST with respect to the structures around it and to develop a safer surgical method that will diminish the potential risk of CST injury. In this study, 30 cadavers from the Department of Forensic Medicine were dissected to observe the surgical anatomy of the CST. The cadavers used in this study were fresh cadavers chosen at 12-24 h postmortem. The levels of superior and intermediate ganglions of cervical sympathetic chain were determined. The distance of the sympathetic trunk from the medial border of LCM at C6, the diameter of the CST at C6 and the length and width of the superior and intermediate (middle) cervical ganglion were measured. Cervical sympathetic chain is located posteromedial to carotid sheath and just anterior to the longus muscles. It extends longitudinally from the longus capitis to the longus colli over the muscles and under the prevertebral fascia. The average distance between the CST and medial border of the LCM at C6 is 11.6 +/- 1.6 mm. The average diameter of the CST at C6 is 3.3 +/- 0.6 mm. Superior ganglion of CSC in all dissections was located at the level of C4 vertebra. The length and width of the superior cervical ganglion were 12.5 +/- 1.5 and 5.3 +/- 0.6 mm, respectively. The location of the intermediate (middle) ganglion of CST showed some variations. The length and width of the middle cervical ganglion were 10.5 +/- 1.3 and 6.3 +/- 0.6 mm, respectively. The CST's are at high risk when the LC muscle is cut transversely, or when dissection of the prevertebral fascia is performed. Awareness of the CST's regional anatomy may help the surgeon to identify and preserve it during anterior cervical surgeries.

CT-guided BoNT-A injection of longus colli muscle in anterocollis patients without anterior shift

Anterocollis (AC) is caused by dystonia of superficial and deep cervical muscles. Bilateral contraction of sternocleidomastoid muscles (SCM) normally leads to head retroflexion and chin protraction, but in dystonic anterior shift it leads to head anteversion. Independently, longus colli muscles (LGC) mediate cervicospinal anteflexion and head anteversion. Thus, CT-guided BoNT-A injection of the often hypertrophic LGC is proposed in AC without anterior shift. We report on 10 treatments of LGC in 7 pts. with AC as the main symptom of cervical dystonia. 3 pts. displayed anterior shift, 1 pt. posterior shift, 3 pts. no shift. TWSTRS and chin-brow vertical angle (CBVA) were assessed. Cervical CT showed asymmetric hypertrophy of LGC in pts. without shift but not in pts. with anterior shift. In the latter, bilateral treatment of SCM and anterior scalene muscles improved dystonia. In pts. without shift, treatment of superficial cervical muscles did not sufficiently improve AC, while TC responded well. In these pts., CT-guided injection of the hypertrophic LGC reduced the TWSTRS-subscore for AC by 42% and CBVA by 50%. This improvement of AC lasted longer than with treatment of superficial cervical muscles alone (up to 9 months). By contrast, in a pt. with posterior shift, LGC treatment did not prove beneficial to AC. In AC with anterior shift, SCM should be treated bilaterally, but in AC without anterior shift CT-guided BoNT-A injection of the hypertrophic LGC is strongly recommendable.

Acute longus colli calcific tendonitis causing neck pain and dysphagia

Acute longus colli calcific tendonitis causing neck pain and dysphagia

Symptomatic occlusion at the origin of the vertebral artery treated using external carotid artery–cervical vertebral artery bypass with interposed saphenous vein graft

Background Symptomatic atherosclerotic steno-occlusive diseases of the vertebrobasilar artery portend a poor prognosis and high risk of stroke recurrence despite medical therapy. We describe 5 medically refractory patients with occlusion at the origin of the VA and the distal portion of the cervical VA perfused via muscular collateral vessels who underwent ECA–cervical VA (V 2 segment) bypass with interposed SVG. Methods The ECA was isolated through a linear incision along the anterior portion of the sternocleidomastoid muscles. The ECA was either laterally or medially retracted, the longus colli muscle was dissected, and the anterior wall of the foramen transversarium was partially removed, which exposed the cervical VA. Each end of the SVG was anastomosed to both the VA and the ECA in a side-to-end fashion. Results Surgery proceeded smoothly in all patients without any new neurologic postoperative deficits. Postoperative cerebral angiography demonstrated that the anastomosis was patent. None of the patients developed further brain ischemic events during follow-up periods ranging from 13 to 114 months (mean, 62 months) after surgery. Conclusion The ECA–cervical VA bypass with interposed SVG is useful when the VA is occluded at the origin and when the distal portion of the cervical VA is perfused via muscular collateral vessels of patients with medically refractory ischemic events in the vertebrobasilar territory.

Commentary

Symptomatic atherosclerotic steno-occlusive diseases of the vertebrobasilar artery portend a poor prognosis and high risk of stroke recurrence despite medical therapy. We describe 5 medically refractory patients with occlusion at the origin of the VA and the distal portion of the cervical VA perfused via muscular collateral vessels who underwent ECA–cervical VA (V2 segment) bypass with interposed SVG.The ECA was isolated through a linear incision along the anterior portion of the sternocleidomastoid muscles. The ECA was either laterally or medially retracted, the longus colli muscle was dissected, and the anterior wall of the foramen transversarium was partially removed, which exposed the cervical VA. Each end of the SVG was anastomosed to both the VA and the ECA in a side-to-end fashion.Surgery proceeded smoothly in all patients without any new neurologic postoperative deficits. Postoperative cerebral angiography demonstrated that the anastomosis was patent. None of the patients developed further brain ischemic events during follow-up periods ranging from 13 to 114 months (mean, 62 months) after surgery.The ECA–cervical VA bypass with interposed SVG is useful when the VA is occluded at the origin and when the distal portion of the cervical VA is perfused via muscular collateral vessels of patients with medically refractory ischemic events in the vertebrobasilar territory.

Acute calcific tendinitis of the longus colli: an imaging diagnosis

Acute calcific retropharyngeal tendinitis or longus colli tendinitis is an uncommon benign condition presenting as acute neck pain. Clinically, it can be misdiagnosed as retropharyngeal abscess, traumatic injury, or infectious spondylitis. The diagnosis is made radiographically by calcification anterior to C1-C2 and prevertebral soft-tissue swelling. We present two cases of this uncommon condition to illustrate the classic findings on CT and MRI. In addition to the typical calcifications anterior to C1-C2, we detected a retropharyngeal effusion in both patients and effusions involving both lateral atlantoaxial joints in one patient, which to our knowledge has not been published in the literature. In both patients, the correct diagnosis was established by prospective review of the radiographic studies. Recognition of the pathognomonic imaging appearance allows for easy diagnosis preventing unnecessary tests and treatment.

Repair of cervical esophageal perforation using longus colli muscle flap: a case report of a patient with cervical spinal cord injury

Background context Perforation of the esophagus after anterior cervical spine surgery is a rare, but well-recognized complication. The management of esophageal perforation is controversial, and either nonoperative or operative treatment can be selected. Purpose Several reports have described the use of a sternocleidomastoid muscle flap for esophageal repair. In this case report, we describe a longus colli muscle flap as a substitute for a sternocleidomastoid flap in a patient with an esophageal perforation. Study design Case report. Patient sample A 20-year-old man sustained cervical spinal cord injury, on diving and hitting his head against the bottom of a pool. A C6 burst fracture was observed with posterior displacement of a bone fragment into the spinal canal. The patient exhibited complete paralysis below the C8 spinal segment level. Methods The patient underwent subtotal corpectomy of the sixth cervical vertebra with the iliac bone graft and augmented posterior spinal fixation (C5–7) with pedicle screws. After the primary operation, the patient showed signs of infection such as throat pain, a high fever, and osteolytic change of the grafted bone by cervical radiograph. A second operation was performed to replace the graft bone using fibula. On the day after the operation, food residue was confirmed in the suction drainage tube, suggesting esophagus perforation. A third operation was immediately performed to confirm and treat esophagus perforation, although apparent esophageal perforation could not be detected at the second operation. Because the erosion around the perforation of the esophageal posterior wall was extensive, a longus colli muscle flap transposition was accordingly performed into the interspace between the esophageal posterior wall and the grafted bone in addition to simple suturing of the perforation. Results Neither high fever nor pharyngeal pain has recurred at latest follow-up, 5 years after surgery. Conclusions To the best of our knowledge, this is the first report concerning the use of a longus colli muscle flap for esophageal perforation after anterior cervical spine surgery.

Retropharyngeal Tendinitis: A Rare Differential Diagnosis of Severe Headaches and Neck Pain

Retropharyngeal tendinitis is a rare cause of intense neck pain and occipital headache. It is caused by an aseptic inflammatory process in the longus colli tendon, triggered by deposition of calcium hydroxyapatite crystal. Clinically, it can be misdiagnosed as retropharyngeal abscess, traumatic injury, infectious spondylitis, cervical artery dissection, or even meningitis. The diagnosis is made radiographically by a nearly pathognomonic amorphous calcification anterior to C1-C2 and prevertebral soft tissue swelling. We present a new case of this uncommon condition exhibiting some unusual features.

Differential treatment of sternocleidomastoid and longus colli muscles in anterocollis patients with and without anterior shift

Anterocollis may be caused by dystonic contractions of superficial and deep cervical muscles. Scalene, digastric, omohyoid muscles and platysma are supposed to be main players in anterocollis. Longus colli, longus capitis and sternocleidomastoid muscles have also been implicated in that difficult to treat form of cervical dystonia. Bilateral BoNT-A injection of sternocleidomastoids, however, is often ineffective and may be complicated by dysphagia. Therefore individual anatomical and biomechanical contributions of the anterior cervical muscles to the complex dystonic action in anterocollis need to be evaluated in detail prior to any BoNT-A injection therapy. Physiologically, the sternocleidomastoid muscles cross the coronary cervicospinal plane. Thus, in a neutral position their bilateral contraction usually leads to a retroflexion of the head and an anterior shift of the chin. By contrast, if a dystonic anterior shift is present, the trajectory of the sternocleidomastoid muscles is shifted ventrally. In this position, their bilateral contraction may contribute to an anteversion of the head. Conversely, the longus colli muscles connect the transverse processes of the cervical vertebrae with the ventral facet of the atlas, thereby exerting an anteflexion of the cervical spine and anteversion of the head independently of the sagittal head position.

The use of functional MRI to evaluate cervical flexor activity during different cervical flexion exercises

The purpose of this study was to investigate the recruitment pattern of deep and superficial neck flexors evoked by three different cervical flexion exercises using muscle functional MRI. In 19 healthy participants, transverse relaxation time (T2) values were calculated for the longus colli (Lco), longus capitis (Lca), and sternocleidomastoid (SCM) at rest and following three exercises: conventional cervical flexion (CF), craniocervical flexion (CCF), and a combined craniocervical flexion and cervical flexion (CCF-CF). CCF-CF gave the highest T2 increase for all muscles. CCF displayed a significantly higher T2 increase for the Lca compared with the Lco and the SCM. When comparing the CCF and CF, no significant difference was found for the Lca, whereas the Lco and SCM displayed a higher T2 increase during CF compared with CCF. This study shows that muscle functional MRI can be used to characterize the specific activation levels and recruitment patterns of the superficial and deep neck flexors during different cervical flexion exercises. During CCF-CF, all synergists are maximally recruited, which makes this exercise useful for high-load training. CCF may provide a more specific method to assess and retrain Lca muscle performance compared with CF and CCF-CF. This study highlights the need to differentiate between the Lco and Lca when evaluating their function, since these results demonstrate a clear difference in activation of both muscles.

Refinement of interbody implant testing in goats: a surgical and morphometric rationale for selection of a cervical level

The authors provide a surgical description of the ventral approach to the cervical spine in a goat model and identify selection of the most appropriate level for testing interbody devices. These constructs are designed for implantation in humans during anterior cervical discectomy and fusion. Such description and guidelines for level selection have never been published in either the medical or veterinarian literature. The study comprised three phases: surgical, anatomical, and morphometric. Six goats underwent ventral approaches and were later killed; their necks were dissected and the cervical spines were processed to obtain clean specimens of the vertebral bodies. Measurements were made at each level using a contact digitizer. The anterolateral bone spurs, called alar processes, and the increased thickness of the longus colli muscle are the surgically relevant characteristics in the goat. The morphometric analysis showed that C2-3 is the most suitable level for implantation of interbody devices. The vertebral endplates at the C2-3 level are relatively flat and parallel to each other, and are perpendicular to the spinal canal axis. More distally, the endplates adopt a more curved arrangement, and the endplate angle becomes significantly greater than 90 degrees. The authors describe anatomical landmarks that are important to safely and effectively perform a ventral cervical spinal approach in the goat. The authors' model identifies C2-3 as the most appropriate level for animal testing of cervical implants because of its similarity to human anatomy. Further study with rigorous biomechanical range of motion evaluation of each caprine cervical level is needed.

Retropharyngeal calcific tendonitis

Calcific tendonitis of the longus colli muscle is an uncommon cause of sudden onset of neck pain. Differential diagnosis should include retropharyngeal abscess, traumatic injury or even meningitis. Diagnosis can be made radiographically with plain radiograph which reveals an amorphous calcification anteriorly to C1-C2 and severe swelling of the prevertebral soft tissue. Treatment of choice is conservative and consists of administration of nonsteroidal anti-inflammatory drugs. Clinically the complaints disappear after 1-2 weeks. Follow-up radiographs are, in fact, unnecessary but demonstrate complete resolution of the calcific density and normalization of the prevertebral swelling.

Metric and morphological study of the upper cervical spine from the Sima de los Huesos site (Sierra de Atapuerca, Burgos, Spain)

In this article, the upper cervical spine remains recovered from the Sima de los Huesos (SH) middle Pleistocene site in the Sierra de Atapuerca (Burgos, Spain) are described and analyzed. To date, this site has yielded more than 5000 human fossils belonging to a minimum of 28 individuals of the species Homo heidelbergensis. At least eleven individuals are represented by the upper cervical (C1 and C2) specimens: six adults and five subadults, one of which could represent an adolescent individual. The most complete adult vertebrae (three atlases and three axes) are described, measured, and compared with other fossil hominins and modern humans. These six specimens are associated with one another and represent three individuals. In addition, one of these sets of cervical vertebrae is associated with Cranium 5 (Individual XXI) from the site. The metric analysis demonstrates that the Sima de los Huesos atlases and axes are metrically more similar to Neandertals than to our modern human comparative sample. The SH atlases share with Neandertals a sagittally elongated canal. The most remarkable feature of the SH (and Neandertal) axes is that they are craniocaudally low and mediolaterally wide compared to our modern male sample. Morphologically, the SH sample shares with Neandertals a higher frequency of caudally projected anterior atlas arch, which could reflect greater development of the longus colli muscle. In other features, such as the frequency of weakly developed tubercles for the attachment of the transverse ligament of the atlas, the Sima de los Huesos fossils show intermediate frequencies between our modern comparative samples and the Neandertals, which could represent the primitive condition. Our results are consistent with the previous phylogenetic interpretation of H. heidelbergensis as an exclusively European species, ancestral only to H. neanderthalensis.

Anatomic mapping and evaluation of the esophagus in relation to the cervical vertebral body

The relationship of the esophagus to the cervical vertebral body (CVB), disc space and longus colli (LC) muscles, to our knowledge, has not been previously studied. The purpose of this study was to quantify the relationship of the esophagus to the CVB, disc space and LC. 30 patients were selected for a retrospective review of computed tomography (CT) scans. Measurements between the esophagus and the C5, C6, and C7 vertebral bodies as well as the C5/6 and C6/7 disc spaces were performed in the midline, 3 mm right and left of midline, and at the edge of the LC on both sides. The closest distance of the esophagus to the CVB and disc space occurs at the midline (range 1.02-1.31 mm at each level). The furthest distance occurred at the edge of the right LC (range 2.67-3.30 mm at each level). The mean distance from the edge of the right LC to the midline was significantly greater (P < 0.01) than mean distance from the edge of the left LC to the midline. No statistical significant differences were observed when comparing measurements at the individual vertebral bodies and disc spaces. The results of the study demonstrate that the esophagus lies in closest proximity to the CVB and disc space in the midline. A larger potential space exists between the esophagus and the CVB and disc space at the edge of the LC. These results may provide insight into a potential cause of post-operative dysphagia. Furthermore, it may help guide the future design of cervical plates to better utilize the potential space between the esophagus and the CVB and disc space at the edge of the LC.

The crowned dens syndrome. Evaluation with CT imaging

The purpose of this study was to verify the value of computed tomography (CT) in the diagnosis of the "crowned dens" syndrome, not only in crystal deposition diseases, but also in other rheumatic or nonrheumatic conditions. Thirty-eight patients (15 men and 23 women; mean age 55 years; age range 35-79) with neck pain were examined and divided into two groups: (1) patients already identified as rheumatic and referred for further investigation of the atlantoaxial region; (2) patients with symptoms confined to the cervical spine, with inconclusive radiographic findings. Unenhanced CT of the cervical spine (Tomoscan SR 7000 Philips, Eindhoven, Netherlands) was performed in all patients. There were 11 cases of rheumatoid arthritis (ten women and one man), two calcium pyrophosphate dihydrate crystal deposition disease (both women), one of systemic sclerosis (a woman), one of osteoarthritis (a man), one of seronegative arthritis (a man), four of neoplasm (one woman and three men) with suspected cervical involvement, one (a man) of haematological disease (lymphoma), one (a woman) of menopausal osteoporosis, ten (five men and five women) of recent or previous trauma with suspected involvement of the skull base and first cervical vertebrae and six of unknown painful cervical dysfunction (three men and three women). CT demonstrated calcific deposits around the dens in 12 patients (three men and nine women), in the transverse and alar ligaments, and in the anterior atlantooccipital membrane. CT revealed horseshoe- or crown-like calcification surrounding the odontoid process. In our series, other rheumatic diseases, especially rheumatoid arthritis, showed similar irregular calcifications of the atlantoaxial joint. Discussion. In calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, the spine may be the only site of involvement, generally asymptomatic. Crystals located in the transverse ligament of the atlas give rise to the crowned dens syndrome, usually in patients affected by severe degenerative lesions of the atlantoaxial joint and peripheral chondrocalcinosis. Symptoms may be absent, or a neurological compressive syndrome may develop. Symptoms tend to worsen with age. The diagnosis is not always easy, as the symptoms are similar to those of other diseases, such as meningitis, cervicobrachial pain, occipitotemporal headache, calcific tendinitis of the longus colli muscle, spondylodiscitis and retropharyngeal abscess. CT is the gold standard in identifying crowned dens syndrome, as it is able to depict the shape and site of calcification and any bone erosions. Radiography of other joints (wrist, knee, pubic symphysis) may help to ascertain whether the disease is due to calcium pyrophosphate dihydrate or hydroxyapatite crystals, and is therefore recommended for routine patient management. Magnetic resonance imaging (MRI) is indicated for the study of neurological complications.