Kinematics of the freely moving head and neck in the alert cat

In this study we examined connections between the moment-generating capacity of the neck muscles and their patterns of activation during voluntary head-tracking movements. Three cats lying prone were trained to produce sinusoidal (0.25 Hz) tracking movements of the head in the sagittal plane, and 22.5 degrees and 45 degrees away from the sagittal plane. Radio-opaque markers were placed in the cervical vertebrae, and intramuscular patch electrodes were implanted in five neck muscles, including biventer cervicis, complexus, splenius capitis, occipitoscapularis, and rectus capitis posterior major. Videofluoroscopic images of cervical vertebral motion and muscle electromyographic responses were simultaneously recorded. A three-dimensional biomechanical model was developed to estimate how muscle moment arms and force-generating capacities change during the head-tracking movement. Experimental results demonstrated that the head and vertebrae moved synchronously, but neither the muscle activation patterns nor vertebral movements were constant across trials. Analysis of the biomechanical model revealed that, in some cases, modification of muscle activation patterns was consistent with changes in muscle moment arms or force-generating potential. In other cases, however, changes in muscle activation patterns were observed without changes in muscle moment arms or force-generating potential. This suggests that the moment-generating potential of muscles is just one of the variables that influences which muscles the central nervous system will select to participate in a movement.     

The correlation between surface measurement of head and neck posture and the anatomic position of the upper cervical vertebrae

STUDY DESIGN: Repeated measurements were made of surface postural angles registering the relative positions of the head and neck in photographs and of angles of the upper cervical vertebrae recorded in lateral cephalometric radiographs in the same subjects. For all registrations, subjects assumed the natural head rest position. OBJECTIVES: To examine the correlation between external measurement of head and neck posture and the anatomic positions of the upper four cervical vertebrae. SUMMARY OF BACKGROUND DATA: Interpretation of surface cervical posture measurement is confounded by lack of knowledge about the extent of the underlying compensatory adjustments among the upper cervical vertebrae that may accompany variation in head and neck posture. The correlation between surface measurement and postural characteristics of the upper cervical spine has not been reported to date. METHODS: The association between a set of angles describing the anatomic position of the four upper cervical vertebrae on lateral cephalometric radiographs and a surface measurement of head and neck posture, the craniovertebral angle, was studied in 34 young adult women aged between 17.2 and 30.5 years, mean age, 24.5 years. Anatomic positions of the upper four cervical vertebrae were expressed by angles relative to the true vertical or horizontal. Surface angles registering head and neck position for each subject were obtained from photographs recorded on two occasions. RESULTS: No strong correlation could be established between the angles taken from the lateral cephalometric radiographs measuring the extent of upper cervical lordosis, orientation of the atlas, vertebral inclination, or odontoid process tilt and surface angles recording head and neck position. This finding was attributed principally to the much greater positional variability demonstrated within the upper cervical spine when compared with the surface measurements of head and neck position. CONCLUSION: Anatomic alignment of the upper cervical vertebrae cannot be inferred from variation in surface measurement of head and neck posture. This is the case even in those people identified with more extreme head and neck postural tendencies.     

长时间颈部前屈对颈部肌肉疲劳的影响

长期颈部前屈对颈椎造成严重影响。为定量评估长时间低头对颈椎疲劳造成的影响，选取20名健康受试者，保持低头角度40°～60°持续3 h。选择胸锁乳突肌，颈部夹肌和肩部斜方肌测量其表面肌电信号。经滤波、整流、振幅标准化等处理后，对每60 s的肌电值进行积分和求其平均功率频率。研究发现，积分肌电值的波动变化具有规律性，首次增大后的减小表征肌肉进入疲劳状态；不同肌肉的平均功率频率(mean power frequency，MPF)值具有明显差异，决定着该肌肉疲劳耐受性的持续时间，且在整个颈部前屈过程中MPF并非简单的线性关系。提出用MPF的导数来提取疲劳特征，用窗口化的MPF负数累积判定肌肉疲劳。结果表明，MPF负数累积能很好地判断肌肉疲劳，胸锁乳突肌在20 min内出现最终疲劳，而颈部夹肌和肩部斜方肌在20 min左右出现了短暂性疲劳，随后在75～100 min时又出现了最终疲劳。因此建议持续颈部前屈时长不超过20 min。      

Electromyographic activity of the cervical musculature during dynamic lateral bending

STUDY DESIGN: Electromyographic profiles from the neck muscles of five young, healthy men were obtained to study the muscular, activation patterns during dynamic external loading. OBJECTIVES: To examine the myoelectric activity of selected cervical muscles during dynamic loading, and to explore the reaction of the cervical muscles to different loading conditions. SUMMARY OF BACKGROUND DATA: The response of cervical muscles throughout dynamic external loading is not well understood. Electromyography provides information, within certain limitations, about the neural drive to various components of the musculature. Such information on activation, combined with geometric parameters of the musculoskeletal tissues, constitutes a tool for helping to understand the mechanism of head and neck impact-related injury. METHODS: Subjects were tested with the head and neck in the neutral and prebent positions. Dynamic loads were applied laterally to each subject by free-falling masses to create peak dynamic loads ranging from about 40 to 100 N. Force and electromyographic data were recorded, and cross-correlations from linear envelope electromyography were calculated. RESULTS: The peak electromyogram showed large differences between the two applied loads and between subjects. There were time delays (75-165 msec) between the peak applied force and the peak electromyogram. The muscles on the contralateral side demonstrated different electromyographic profiles between subjects. Within subjects, the electromyographic profiles from each muscle were consistent for the same trial conditions. CONCLUSIONS: Electromyographic profiles and the cross-correlator coefficients for cervical muscles have shown reproducible intrasubject muscle synergies, which were not sensitive to the magnitude of applied load and the posture of the head. Intersubject muscle activity patterns varied.     

Distribution of motoneurons supplying feline neck muscles taking origin from the shoulder girdle

A combination of fluorescent retrograde tracers and horseradish peroxidase (HRP) was used to compare the spinal distributions of motoneurons supplying shoulder muscles with attachments to the skull and cervical spinal cord that suggest a significant role in head movement. Two muscles, the rhomboideus and the levator scapulae, were innervated by multiple segmental nerve bundles that entered the muscles at different rostrocaudal locations. Motoneurons that were labelled retrogradely from rhomboideus nerve bundles formed a single, long column in the ventral horn from C4 to C6, lateral to previously studied motor nuclei supplying deep neck muscles. When different tracers were used to differentiate motoneurons supplying specific nerve bundles, discrete subnuclei could be identified that were organized in a rostrocaudal sequence corresponding to the rostrocaudal order of the nerve bundles. Levator scapulae motoneurons formed a second elongate column immediately lateral to the rhomboidues motor nucleus. Three other muscles, that trapezius, sternomastoideus, and cleidomastoideus, were supplied by cranial nerve XI. Labelled motoneurons from these muscles formed a single column from the spinomedullary junction to middle C6. Within this column, the three motor nuclei supplying the sternomastoideus, cleidomastoideus, and trapezius were laminated mediolaterally. Sternomastoideus and cleidomastoideus motoneurons were confined to upper cervical segments, whereas trapezius motoneurons were found from C1 to C6. In C1 and C6, the motoneuron column was located centrally in the gray matter, but, between C2 and C5, the column lay on the lateral wall of the ventral horn in a position dorsolateral to motor nuclei supplying the rhomboideus and the deeper neck muscles. The findings in this study suggest that descending and propriospinal systems responsible for coordinating head movement may have to descend as far caudally as C6 if they are to project onto muscles controlling the mobility of the lower neck.     

Probable torticollis revealed in decapitated skull

The skeletal features of a moderately decomposed decapitated head recovered in 1993 are consistent with torticollis (wryneck) and inconsistent with other possible syndromes. Asymmetries of the face, cranial vault, mandible, and cervical vertebrae closely resemble published cases of paleopathological and recent torticollis. The laterally directed left occipital condyle and articulation of the basicranium and cervical vertebrae indicate that the head was tipped toward the left shoulder. Right-left asymmetries of areas of muscular attachments are compatible with a leftward head deviation. Mild arthritis of the atlantal-occipital and intervertebral joints, clinoid bridging, and thickening of the inner table of the frontal squamosa may not be related to the possible torticollis. The postural deviations of the head and neck may aid in the identification of this homicide victim, as did skeletal evidence to torticollis in an earlier case from Britain.     

Influence of head position on dorsal neck muscle efficiency

The aim of this study was to assess the influence of head position on dorsal neck muscle efficiency in the sagittal plane. Fifteen subjects participated. The EMG versus isometric extension moment of dorsal neck muscles was studied in neutral (with subject gazing on a horizontal plane), cervical flexed, and cervical extended positions. A vectorial construction was created by means of photographs to calculate the extension moment which balances measured pulling force and gravitational force in isometric conditions. The maximum extension was highest in neutral position. The EMG/moment relationship was non-linear. The ratio between the EMG and the generated moment differed significantly in the three positions (p < 0.01) and was lower in neutral position. These results demonstrate the influence of head position on dorsal neck muscle efficiency; muscles appeared most efficient in neutral position. Muscle length, depending on head position, is probably the main influencing factor.     

The effect of triple pelvic osteotomy on the articular contact area of the hip joint in dysplastic dogs: an in vitro experimental study

This study compares the frequency of signs and symptoms from the cervical spine in 24 patients diagnosed with Meniere's disease and 24 control subjects from a population sample. From a previous controlled comparative study concerning signs and symptoms of craniomandibular disorders, 24 patients diagnosed with Meniere's disease (10 males and 14 females) and their 24 matched control subjects participated in this investigation on the state of the cervical spine. Symptoms of cervical spine disorders, such as head and neck/shoulder pain, were all significantly more frequent in the patient group than in the control group. Most of the patients (75%) reported a strong association between head neck movements in the atlanto-occipital and atlanto-axial joints and triggered attacks of vertigo. Also, 29% of the patients could influence their tinnitus by mandibular movements. Signs of cervical spine disorders, such as limitations in side-bending and rotation movements, were significantly more frequent in the patient group than in the control group. Tenderness to palpation of the transverse processes of the atlas and the axis, the upper and middle trapezius, and the levator scapulae muscle were also significantly more frequent in the patient group. The study shows a much higher prevalence of signs and symptoms of cervical spine disorders in patients diagnosed with Meniere's disease compared with control subjects from the general population.     

Neurophysiological investigations in patients with head tremor

We studied 30 patients whose primary complaint was head tremor in an attempt to characterize neurophysiological aspects of their abnormal movement. Based on family medical history and physical examination, 23 patients had definite or probable essential tremor (essential head tremor, EHT). The remaining seven had mild dystonic signs accompanying their head tremor (head tremor plus dystonic signs, HT + DS). We recorded head movement and the electromyographic (EMG) activity of the sternomastoid and splenius capitis muscles, determined the spontaneous blinking rate, and measured the excitability recovery curve of the blink reflex and of the masseteric inhibitory reflex. All patients had tremor bursts at a frequency ranging between 3 and 9 Hz in at least one of the muscles examined. The predominant pattern seen when patients were sitting relaxed and facing forward was that of synchronized EMG bursts in both splenius capitis muscles. Maintenance of extreme head postures demonstrated two types of additional abnormalities: type 1 (enhancement of tremor), which was observed in 11 patients (47.8%) with EHT and in two (28.5%) with HT + DS; and type 2 (activation of neck muscles not required for maintenance of the posture), which was observed in two patients (8.7%) with EHT and in five (71.5%) with HT + DS (chi 2 = 26.4; p < 0.001). Mean blinking rate per minute was 24.9 +/- 14.6 in patients with EHT and 42.3 +/- 10.5 in patients with HT + DS (paired t test, p = 0.001). The blink reflex and masseteric inhibitory reflex excitability recovery curves showed an abnormal interneuronal excitability enhancement in seven (30.4%) of the 23 patients with EHT and in two (28.5%) of the seven with HT + DS (chi 2 = 3.1; p > 0.05). Abnormal patterns of EMG activity of the neck muscles correlated well with the presence of mild dystonic signs. However, the analysis of brainstem interneuronal excitability did not enable recognition of those patients with head tremor who could potentially develop cervical dystonia. The enhancement of brainstem interneuronal excitability found in approximately 30% of patients with head tremor could be related to plastic changes triggered by increased activity of the cranial muscles.     

The anterolateral structures of the neck and trunk

This work has in view the arrangement of the elements that form the anterolateral wall of the neck, thorax and abdomen. We insist on the behavior of the fasciae and the situation of the connective spaces related at the muscular layers that enter the structure of this segments. We have found the continuity of the deep cervical fascia (the superficial fascia, after the French anatomy), like a muff that surrounds the neck and the trunk; in the places where this deep cervical fascia is related to the bones (for example, the clavicle), it is continued by the periosteum. On the ventral midline, the deep cervical fascia is very dense and resistant and it is continued from the hyoid bone to the pubis. It is adherent on the connective deep elements, taking part at the formation of the "linea alba". On the posterior midline it is adherent at the fibrous elements that fix the fascia on the spinous process of the vertebrae. At the level of the neck, this fascia is very obvious and resistant; it becomes thinner according as it descent to the abdomen. At the cervical level it surrounds the sternocleidomastoid and the trapezius, at the level of the thorax it surrounds the pectoralis major and the latissimus dorsi, at the level of the abdomen it becomes very fine and it covers the rectus sheath in the anterior part; at the level of the obliquus externus abdominis is very difficult to demonstrate its existence. We followed then the behavior of the anterolateral muscles from the cervical and the abdominal segments. We have found the continuity of the anterior paramedian muscles: the first plane--the sternocleidomastoid, pectoralis major (its sternal fibres form the right sternal) and the rectus abdominis and pyramidalis. For the first and second planes we make an analogy between the muscles of the neck, the subclavius, pectoralis minor, serratus anterior. The second plane--the infrahyoid muscles, the subclavius, pectoralis minor, serratus anterior. The third plane--the scaleni, anterior, medius and posterior, intercostales, transversus thoracis, obliquus externus abdominis, obliquus internus abdominis and transversus abdominis. This work excludes the suprahyoid muscles--their origin, function, innervation and vascularization are debated in another study.     

Oxygenation status of squamous cell carcinoma of the head and neck: comparison of primary tumors, their neck node metastases and normal tissue

AIM: Investigation of the relationship between the pO2-status of primary tumors, their cervical neck node metastases and normal tissues in squamous cell carcinomas of the head and neck. PATIENTS AND METHODS: Pretreatment oxygenation of primary tumors, their neck node metastases and of the contralateral sternocleidomastoid muscle was assessed in 16 patients with histologically proven advanced squamous cell carcinomas of head and neck. Oxygenation was measured with a polarographic microelectrode system (Eppendorf-pO-Histograph). Using CT/MRT additionally the volume of the tumors was estimated. RESULTS: A highly significant correlation existed between the median pO2 of primary tumors and their neck node metastases and between the relative proportion of hypoxic values (< 5 mm Hg) of both anatomic sites (both p = 0.0001) (Figure 1). Primary tumors were not different from their neck node metastases, neither regarding the pO2 median values nor in view of the relative frequency of hypoxic values (Table 1). No correlation was found between the volume of primary tumors and the one of their neck node metastases. For volume of tumors and the oxygenation status no relationship was found as well. Significantly different was the median pO2 in the muscles from the one of the malignant tissues (p = 0.0004). CONCLUSION: The results suggest that for to estimate the oxygenation status of squanious cell carcinomas of the head and neck pO2 measurements of primary tumors and neck node metastases are equally sufficient.     

The surgical anatomy of the long muscles of the neck and head and the potentials for their use in reconstructive operations on the palatopharyngeal sphincter

The authors analyze the results of topographoanatomic studies of the prevertebral muscles of the neck, carried out in 37 nonfixed human corpses. They substantiate the possibility of leaving intact the vasculonervous branches in cutting and translocating towards the soft palate of the grafts on an upper peduncle from long muscles of the neck and head.     

There are no racial, age, sex, or weight differences in the effect of salt on blood pressure in salt-sensitive hypertensive patients

STUDY DESIGN: A bench-top trauma sled was used to apply four intensities of whiplash trauma to human cadaveric cervical spine specimens and to measure resulting intervertebral rotations using high-speed cinematography. OBJECTIVES: To determine the cervical spine levels most prone to injury from whiplash trauma and to hypothesize a mechanism for such injury. SUMMARY OF BACKGROUND DATA: Whiplash injuries traditionally have been ascribed to hyperextension of the head, but other mechanisms such as hypertranslation also have been suggested. METHODS: Six occiput to T1 (or C7) fresh cadaveric human spines were studied. Physiologic flexion and extension motions were recorded with an Optotrak motion analysis system by loading up to 1.0 Nm. Specimens then were secured in a trauma sled, and a surrogate head was attached. Flags fixed to the head and individual vertebrae were monitored with high-speed cinematography (500 frames/sec). Data were collected for 12 traumas in four classes defined by the maximum sled acceleration. The trauma classes were 2.5 g, 4.5 g, 6.5 g, and 8.5 g. Significance was defined at P < 0.01. RESULTS: In the whiplash traumas, the peak intervertebral rotations of C6-C7 and C7-T1 significantly exceeded the maximum physiologic extension for all trauma classes studied. The maximum extension of these lower levels occurred significantly before full neck extension. In fact, the upper cervical levels were consistently in flexion at the time of maximum lower level extension. CONCLUSIONS: In whiplash, the neck forms an S-shaped curvature, with lower level hyperextension and upper level flexion. This was identified as the injury stage for the lower cervical levels. A subsequent C-shaped curvature with extension of the entire cervical spine produced less lower level extension.     

Study of the olfactory effects of citronellal in the environmental air

The study was performed using four cadavers of adult persons with the method of preparation. The access to the ligament was obtained by the removal of the inferior orbital wall and inferior orbital adiposal layer. Topographical anatomy of Lockwood ligament, its interrelations with inferior rectus and oblique muscles and attachment to lateral and medial orbital walls were studied. Lockwood ligament, the transverse fascial structure that supports the eyeball, stabilizes it, providing the framework for inferior rectus and oblique muscles of the eye.     

Leg ulcers: finding solutions to common problems

29 cadaveric specimens of head and neck obtained from adults of both sexes following fixation in 5% formaldehyde were the material for the study. 43 samples of cervical ansa were examined. The investigation demonstrated that in the majority of cases (60.5%) cervical ansa was located exterior to internal jugular vein. The variants with the high position of cervical ansa in respect to the upper margin of thyroid cartilage were found in the samples with cervical ansa lying interiorly to the internal jugular vein.     

The ligamento-muscular stabilizing system of the spine

STUDY DESIGN: Electrical and mechanical stimulation of the lumbar supraspinous ligament of three patients with L4-L5 spinal deficits and of the feline model, respectively, was applied while recording electromyography on the multifidus muscles. OBJECTIVES: To determine if mechanoreceptors in the human spine can reflexively recruit muscle force to stabilize the lumbar spine, and to demonstrate, in the feline model, that such ligamento-muscular synergy is elicited by mechanical deformation of the lumbar supraspinous ligament (and possibly of other spinal ligaments), the facet joint capsule, and the disc. SUMMARY OF BACKGROUND DATA: The literature repeatedly confirms that ligaments have only a minor mechanical role in maintaining spine stability, and that muscular co-contraction of anterior and posterior muscles is the major stabilizing mechanism of the spine. The literature also points out that various sensory receptors are present in spinal ligaments, and that the ligaments are innervated by spinal and autonomic nerves. Data that describe how ligaments and muscles interact to provide stability to the spine were not found. METHODS: The supraspinous ligament at L2-L3 and L3-L4 was electrically stimulated in three patients undergoing surgery to correct deficits at L4-L5. Electromyography was performed from the multifidus muscles at L2-L3 and L3-L4, bilaterally. In 12 cats, the supraspinous ligaments from L1-L2 to L6-L7 were mechanically deformed, sequentially, while electromyography was performed from the multifidus muscles of the six levels. Loading of the ligament was applied before and after each of the two vertebrae were externally fixed to prevent motion. RESULTS: Electromyograms were recorded from the multifidus muscles, bilaterally, in the two of the three patients, demonstrating a direct relationship to receptors in the supraspinous ligament. Electromyograms were recorded from the feline multifidus muscle with mechanical loading of the supraspinal ligament at each of the L1-L2 to L6-L7 motion segments. In the free-spine condition the largest electromyographic discharge was present in the level of ligament deformation, and lower electromyographic discharge was recorded in two rostral and caudal segments. After immobilizing any two vertebrae, loading of the ligament resulted in electromyographic discharge in the muscles of the same level and at least one level above and/or below. CONCLUSIONS: Deformation or stress in the supraspinous ligament, and possibly in other spinal ligaments, recruits multifidus muscle force to stiffen one to three lumbar motion segments and prevent instability. Strong muscular activity is seen when loads that can cause permanent damage to the ligament are applied, indicating that spastic muscle activity and possibly pain can be caused by ligament overloading.     

Organization of single motor units in feline sartorius

1. We depleted single motor units in feline sartorius muscles of glycogen by stimulating their motoneurons intracellularly. We mapped the intramuscular distribution of depleted fibers by inspecting histological cross-sections throughout the length of sartorius. 2. We selected ten depleted motor units for detailed study and quantitative analysis. Nine motor units were located in the anterior head of sartorius. One was located in a muscle whose distal half appeared to have been damaged some time before the acute experiment. A single motor unit was located in the medial head of sartorius. 3. Five motor units were composed of fast-twitch glycolytic (FG) muscle fibers, two of fast-twitch oxidative glycolytic (FOG) muscle fibers, and three of slow-twitch oxidative (SO) muscle fibers. Estimates of the numbers of depleted fibers in motor units of anterior sartorius indicated that FG motor units were larger (mean 566 fibers) than FOG and SO motor units (SO mean 190, FOG mean 156 fibers). The SO motor unit in the damaged muscle had 550 fibers. One motor unit depleted in the medial head of sartorius had 270 fibers with FG profiles. 4. Muscle fibers belonging to each anterior motor unit were never distributed throughout the whole cross-section of anterior sartorius at any proximodistal level. Furthermore, fibers were distributed nonuniformly along the proximodistal axis of the muscle. In most muscles at least a few depleted fibers were found at all proximodistal levels. However, in one normal muscle and the damaged muscle, depleted fibers were confined to the proximal end. 5. The fibers in the medial motor unit were confined to a strip that did not extend across the whole cross-section of the muscle head. Fibers within this strip were scattered quite evenly from origin to insertion. This medial FG motor unit occupied a smaller territory and contained fewer fibers than anterior motor units of the same histochemical type. 6. These results show that sartorius motor units are not distributed uniformly in the mediolateral plane; those in anterior sartorius were distributed asymmetrically in the proximodistal axis as well. This finding has important functional implications for the way in which we model force development and transmission in sartorius and other long muscles.     

Endometriosis: medical and surgical intervention

BACKGROUND: Multiple primary neoplasms have been reported 4% to 26% of patients with a squamous cell carcinoma (SCC) of the head and neck. The vast majority of these second primaries are SCC and occur in the upper aerodigestive tract; however, head and neck SCC patients are also at higher risk for nonepidermoid neoplasms at any site. Reticuloendothelial malignancies (REM) have been reported in many patients that have SCC of the head and neck as well. METHODS: Retrospective case series of 5 advanced cases of SCC of the head and neck with synchronous REM. RESULTS: There was 40% mortality with 19.4 months mean follow-up. Fifty percent of the case had simultaneous cervical involvement with both processes. CONCLUSION: REM can occur simultaneously with SCC of the head and neck and confound staging of nodal status. Head and neck SCC patients are at increased risk for REM secondary to age and treatment factors.     

Mechanism of head and neck response to -Gx impact acceleration: a math modeling approach

Mathematical modeling has attained wider acceptance in recent years. In particular, the use of computer programs to simulate the dynamic response of a human in a crash situation has become an attractive alternative to full-scale experimental testing. This paper analyzes data on the dynamic response of the living human head and neck to -Gx impact acceleration, where the motion of the subject's head and neck in the midsagittal plane was monitored with inertial instrumentation and high-speed photography for confirmation. The Calspan "3D Computer Simulator of Motor Vehicle Crash Victims" was used to predict expected responses for the deceleration pulses employed. These estimates were compared to the fully instrumented human test runs. The standard 15-segment and 14-joint representation of the occupant was modified to include two sternoclavicular joints, increasing the articulation in the upper torso. Analysis of the data indicated that muscular activity in the head and neck seemed to be evident and does influence motion of the head, even at relatively high (10-G peak, 530 G/s onset) acceleration levels. Simulation of muscular contraction, using a spring-damper arrangement, improved the results significantly. Additionally, possible limitations to head-to-neck motion, such as ligament restrictions, were also modeled.     

The cervical spine in the skeletal dysplasias and associated disorders

The cervical spine is an especially important area, not only for the diagnosis of the skeletal dysplasias, but also for the management of the patient. By the "cervical spine" I refer not only to the vertebral bodies and posterior elements of this region, but also to the neural elements contained within, especially the cervical cord. The spine is supported by a group of ligaments both anteriorly and posteriorly, with special fixation of the odontoid and C2 by a ligament which normally affixes it firmly to C1. Multiple things may go wrong with the development of the cervical spine. There may be abnormal development of the "vertebrae" in this region, ranging from hypoplasia to developmental failure and/or abnormal ossification of the cervical vertebrae; associated or unassociated odontoid hypoplasia; poor ligamental fixation of C2 resulting in C1-2 subluxation; abnormal development of the posterior processes; abnormal ligamental development or laxity with abnormal cervical kyphosis or lordosis; and, in the case of more fragile/brittle bone development (osteoporosis or increased bone density), fractures can lead to cervical spine problems. The skeletal dysplasias that involve cervical spine problems constitute about 35 of the 150 well-described disorders. These include certain families of disorders like the type II collagenopathies, as well as many individual disorders. It is very important for the clinician to be able to pilot patients through the various appropriate imaging modalities - conventional radiographs of the cervical spine; lateral flexion/extension views; CT; MRI - so that proper management and therapy will result.