Acute Exacerbation of Idiopathic Pulmonary Fibrosis

Figure 1: Baseline chest radiograph of a patient with known idiopathic pulmonary fibrosis (IPF) shows bibasilar coarse reticular opacities, traction bronchiectasis and subpleural opacities.
Figure 2: Chest radiograph performed 3 months later when the patient developed acute dyspnea and hypoxemia shows new groundglass opacities superimposed on areas of pre-existing IPF.

Facts: IPF

• Most common form of idiopathic interstitial pneumonias
• Gradually progressive disease with steady worsening of symptoms, lung function and gas exchange
• Median survival 3 years, no current treatment proven effective

Facts: Acute Exacerbation of IPF

• Some patients with IPF develops acute respiratory deterioration, which is an unusual natural course of diseases
• Idiopathic, no identifiable cause (infection, heart failure or pulmonary embolism)
• This can occur at anytime during the disease course, and can be a presenting symptom of IPF
• More common in men
• Acute to subacute worsening of dyspnea, generally within 30 days, fever, cough, flulike symptoms, severe hypoxemia, respiratory failure requiring mechanical ventilation, low PaO2/FiO2 ratio

Imaging Features

• Bilateral groundglass opacities with or without consolidation, superimposed on pre-existing IPF
• Groundglass opacities can be peripheral, multifocal or diffuse (pathology from surgical lung biopsy usually shows diffuse alveolar damage)
• Differential diagnosis on imaging: pulmonary edema, pneumonia superimposed on IPF

Diagnostic Criteria

• Previous or concurrent diagnosis of IPF
• Unexplained worsening or development of dyspnea within 30 days
• HRCT with new bilateral groundglass abnormality and/or consolidation superimposed on a background reticular or honeycomb patter consistent with IPF
• No evidence of pulmonary infection by endotracheal aspirate or bronchoalveolar lavage
• Exclusion of alternative causes, including the following: left heart failure, PE, identifiable cause of acute lung injury

Reference

Collard HR, Moore BB, Flaherty KR, et al. Acute exacerbations of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med 2007;176:636-643.

Discitis-Osteomyelitis

Figure 1: Lateral chest radiograph of a 76-year-old man with back pain shows destruction of mid-thoracic disc space (star).
Figure 2: Sagittal reformatted CT image (myelogram) shows destruction (star) of the disk space, opposing endplates and epidural extension of soft tissue (arrowheads) seen as filling defect on this myelographic study.

Facts: Spinal Infections

• A spectrum of diseases - osteomyelitis (spondylitis), discitis, discitis-osteomyelitis, epidural abscess
• Of all osteomyelitis, spine accounts for 2% - 4% of anatomic sites
• When spinal infection involves thoracic spine, neurologic compromise is a concern
• Patients at risk include diabetes, IV drug user, chronic delibitating disease, immunosuppression, recent vertebral surgery
• Most common clinical presentation = axial back pain, constant, not relieved by rest (night pain is a red flag for infection or neoplasm)
• Most spinal infections are due to bacterial infection (>50%, S. aureus); definitive diagnosis made by culture from blood or biopsy

Imaging

• Plain radiography: disc space narrowing (2-3 weeks of infection) --> endplate sclerosis (8-12 weeks) --> bony lysis --> vertebral body collapse resulting in localized kyphosis
• CT: more bony details, with myelography it can delineate the degree of spinal canal encroachment
• MRI: best imaging method to assess spinal infection; high sensitivity/specificity/accuracy (more than 90%)
• Features: disc destruction (narrowing, signal change), endplate destruction, abscess, epidural extension, posterior element involvement
• Think of TB if: late clinical presentation, extensive paravertebral abscess, relative preservation of disc, subligamentous spread

Our case: Discitis-osteomyelitis from Staphylococcus aureus.

References:

1. An HS, Seldomridge JA. Spinal infections diagnostic tests and imaging studies. Clin Orthop Rel Res 2006;444:27-33

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Above picture: Singapore's Flyer by Paithoon Wichiwaniwate, M.D.

Zygomaticomaxillary Complex (ZMC) Fracture

Figures 1 & 2: Axial CT images show displaced fractures of the anterior and posterior walls of the right maxillary sinus (arrows), subtle fracture of the right zygomatic arch (short arrow) and a slightly angulated fracture of the lateral wall of the orbit (arrowhead).
Figure 3: 3D CT image shows a complete look of a ZMC fracture, including the fracture of the maxillary walls, zygomatic arch (arrow) and lateral orbital wall at the zygomaticosphenoid suture (arrowheads).

Facts: ZMC Anatomy

• The zygomaticomaxillary complex is a quadrupled structure, meaning that it relates to 4 different bones of the skull: temporal bone, maxilla, frontal bone and skull base
• Paired zygomas each have two attachments to the cranium and two to the maxilla.
• Two major 'buttresses' of the ZMC are: upper transverse maxillary (across zygomaticomaxillary and zygomaticotemporal sutures) and lateral vertical maxillary (across zygomaticomaxillary and zygomaticofrontal sutures).
• In fact, zygoma also relates posteriorly with the sphenoid bone of the skull base

Facts: ZMC Fractures

• Fractures involving this quadrupled structures: anterior maxillary wall, posterolateral maxillary wall, zygomatic arch and lateral orbital wall
• If fracture at the lateral orbital wall is angulated, it often increases orbital volume resulting in enophthalmos)
• If fracture at the zygoma is comminuted, it often requires fixation via a scalp incision to fix the loss of cheek projection and increase facial width
• Frequently missed ZMC fracture is at the temporal bone portion

Imaging Descriptions

• Describe alignment of the zygoma and sphenoid at the lateral orbital wall fracture; angulation here reflects rotation deformity and increased orbital volume that needs to be fixed
• Describe if the fracture along the zygomaticomaxillary suture traverses the infraorbital nerve foramen
• Degree of comminution of zygomatic arch
• Don't forget to look at the temporal bone portion of the ZMC for a fracture

Reference:

Hopper RA, Salemy S, Sze RW. Diagnosis of midface fractures with CT: what the surgeon needs to know. Radiographics 2006;26:783-793.

H1N1 (Swine Flu) Pneumonia

Chest radiograph shows patchy airspace opacities in bilateral mid to lower lung zones in a patient infected with H1N1 virus (lab confirmed), admitted to the ICU. Subsequent CT (not shown) reveals similar findings without pleural effusions or lymphadenopathy.

Facts

• First reported in Mexico in April 2009
• Fatality rate 0.45%
• Confirmed case = a person with an influenza-like illness with laboratory confirmed novel influenza A (H1N1) virus infection by one or more of the following tests: real-time RT-PCR, viral culture
• Influenza-like symptoms = fever, cough, sore throat, body aches, headache, chills, fatigue

Radiographic Appearance

• Initial exam is normal in nearly half of cases who had radiography
• When initial exam is abnormal, the abnormality is patchy consolidation (50%), groundglass opacity or groundglass opacity with consolidation (25%)
• Predominant location: lower lung zones (70%), diffuse (25%)
• Pleural effusion not common (less than 10%)
• Lymphadenopathy uncommon

Based on a single, uncontrolled study:

• Patients with abnormal initial radiograph were associated with admission and severe disease
• H1N1 infection was associated with a high rate of pulmonary embolism (36%) among patients admitted to the ICU

Reference:

Agarwal PP, Cinti S, Kazerooni EA. Chest radiographic and CT findings in novel swine-origin influenza A (H1N1) virus (S-OIV) infection. AJR 2009;193:1488-1493.