Morphological characteristics of diffuse idiopathic skeletal hyperostosis in the cervical spine

<div><p>Objectives</p><p>Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by anterior ossification of the spine and can lead to dysphagia and airway obstruction. The morphology of the newly formed bone in the cervical spine is different compared to the thoracic spine, possibly due to dissimilarities in local vascular anatomy. In this study the spatial relationship of the new bone with the arterial system, trachea and esophagus was analyzed and compared between subjects with and without DISH.</p><p>Methods</p><p>Cervical computed tomography (CT) scans were obtained from five patients with dysphagia and DISH and ten control subjects. The location of the vertebral and carotid arteries, surface area of the hyperostosis and distance between the vertebral body and the trachea and esophagus was assessed in the axial view.</p><p>Results</p><p>The surface area of the newly formed bone was located symmetrically anterior to the vertebral body. The ossifications were non-flowing in the sagittal view and no segmental vessels were observed. Substantial displacement of the trachea/esophagus was present in the group with DISH compared to the controls.</p><p>Conclusions</p><p>The hyperostosis at the cervical level was symmetrically distributed anterior to the vertebral bodies without a flowing pattern, in contrast to the asymmetrical flowing pattern typically found in the thoracic spine. The hypothesis that the vascular system acts as a natural barrier against new bone formation in DISH could be further supported with these findings. The significant ventral displacement of the trachea and esophagus may explain the mechanism of dysphagia and airway obstruction in DISH.</p></div

Examples of emphysema in the explanted lungs (H&E stained slides, magnification 200x).

<p>A-E: Emphysematous changes in patients with CF. A = score 1: some emphysematous changes are present next to a scar in <20% of residual lung tissue. B-D = score 2: emphysematous changes in 20–50% of residual lung tissue, next to scar tissue (B) or in the paraseptal region (C and D). E = Score 3: emphysematous changes in >50% of residual lung tissue. F = Emphysema in an explanted lung of a patient with severe COPD, for comparison.</p

Correlation between lung function parameters and histopathology and quantified CT emphysema score.

<p><i>IN</i>_<i>-950</i> CT emphysema quantified as the percentage of voxels below -950HU in inspiration; <i>FEV</i>_<i>1</i> Forced expiratory volume in the first second; <i>FEV</i>_<i>1</i><i>/FVC</i> ratio of FEV₁ over forced vital capacity; <i>MEF</i>_{<i>25–75</i>} Median flow between 25% and 75% of forced vital capacity.</p><p>Correlation between lung function parameters and histopathology and quantified CT emphysema score.</p

Graphical illustration of the measurements on the CT images.

<p>In (A) the CT scan is shown of a control subject with corresponding illustration (B). The parallel lateral lines are presented in light blue and carotid and vertebral arteries in red. CT scan (C) represents a male subject with DISH (72 years old) and matches illustrations (D and E). The parallel lateral lines (light blue) and the midsagittal anteroposterior (MAP) line (dark blue) were used to compare the different surface areas of newly formed bone (light/dark grey). CT scan (F) shows a male subject with DISH (61 years old) and corresponds to illustrations (G and H). The green lines demonstrate the distances between the center of the vertebral body and the trachea and esophagus, respectively.</p

Patient distribution in the histopathologically defined subgroups.

<p>Emphysema extent was semi-quantitatively scored by two observers in consensus, using a 4-point scale: score 0 (no emphysematous changes); score 1 (0–20% emphysema); score 2 (20–50% emphysema); and score 3 (>50% emphysema). Areas of established fibrosis or bronchiectasis were excluded from the estimation.</p><p>Patient distribution in the histopathologically defined subgroups.</p

Relation between CT Emphysema extent and age.

<p>CT emphysema is defined as the percentage of lung volume with an attenuation of -950 Houndfield Unit or lower (IN_-950).</p

Clinical data of the study population.

<p>Total values are presented as median with interquartile range.</p><p>* Missing data (4 cases)</p><p>^a percentage with exocrine insufficiency</p><p>^b percentage with CFRD</p><p>^c percentage with pseudomonas colonization</p><p><i>IN</i>_<i>-950</i> CT emphysema quantified as the percentage of voxels below -950HU in inspiration</p><p><i>FEV</i>_<i>1</i> Forced expiratory volume in the first second; <i>FEV</i>_<i>1</i><i>/FVC</i> ratio of FEV₁ over forced vital capacity; <i>MEF</i>_{<i>25–75</i>} Mean flow between 25% and 75% of forced vital capacity; <i>CFRD</i> cystic fibrosis related diabetes.</p><p>Clinical data of the study population.</p

Visual grading of structural CF lung disease.

<p>Total scores are presented as median with interquartile range. Scoring is based on Ref 12.</p><p>Values are an overall score for all six lung lobes (lingula considered a separate lobe). % scores of each parameter are the percentage of the total score possible.</p><p><i>BE</i> bronchieactasis; <i>MP</i> Mucusplugging; <i>PBT</i> Peribronchial thickening; <i>PAR</i> Parenchymal (ie. opacity and groundglass); <i>EMPH</i> Emphysema (ie. bullous and non-bullous)</p><p>^a Components scored on a per lobe basis: None, <1/3, 1/3 to 2/3 or >2/3 of the lung lobe (0–3)</p><p>^b Components scored on a per lobe basis: None, mild, moderate or severe (0–3)</p><p>Visual grading of structural CF lung disease.</p

CT emphysema distribution between the semi-quantitative histopathologic emphysema score subgroups.

<p>CT emphysema is defined as the percentage of lung volume with an attenuation of -950 Houndfield Unit or lower (IN_-950).</p

Graphical illustration of the planes used for the measurements.

<p>Measurements were performed at three levels in the C4, C5 and C6 vertebral bodies. The axial CT images were reconstructed to planes parallel to the endplate. (A) Sagittal CT image from a 69 year old male. The illustration (B) shows the three levels (C4, C5, C6) and three transverse locations at C5 (1, 2, 3) that were used for the measurements in the axial plane. The dashed line 1 shows the level adjacent to the cranial endplate, line 2 the mid-vertebral level and line 3 the level adjacent to the caudal endplate. The same approach (using the three lines for the transversal levels) was also used for the C4 and C6 vertebral body.</p