Ehlers-Danlos Syndrome: Comprehensive Imaging Guide and Clinical Overview
Overview
Ehlers-Danlos Syndrome derives its name from the physicians Edward Ehlers and Henri-Alexandre Danlos, who described the condition in the early 20th century based on characteristic skin and joint abnormalities.
The naming rationale emphasizes the core features of tissue fragility and hyperelasticity observed clinically.
Brief clinical findings include joint hypermobility, skin hyperextensibility, easy bruising, and vascular fragility, particularly in the vascular subtype.
Ehlers-Danlos Syndrome follows an autosomal dominant inheritance pattern in its vascular type due to mutations in the COL3A1 gene encoding type III collagen.
Key Imaging Features
- Arterial aneurysms represent the most common finding in Ehlers-Danlos Syndrome, affecting visceral arteries, aorta, and head and neck vessels, often multiple and progressive over time.
- Arterial dissections occur frequently, particularly in medium and large arteries, leading to life-threatening hemorrhage or infarcts in brain, kidney, or spleen.
- Arterial ectasias and tortuosity are prominent, with dolichoectatic intracranial arteries showing enlargement and elongation on CT angiography or MR angiography.
- Arterial occlusions arise from dissection or thrombosis, visible as abrupt cutoffs on ultrasound or CT angiography.
- Nonvascular findings include hemarthrosis, joint instability, and soft tissue fragility with stretched ligaments or cartilage wear on MRI.
- Cerebrovascular abnormalities feature enlarged, tortuous vessels and arteriovenous fistulas in the posterior circulation on maximal intensity projection MR angiography images.
- Spinal manifestations show craniovertebral junction instability, Chiari malformation, or tethered cord on positional MRI, with measurements of atlantoaxial subluxation exceeding 5 mm indicating severity.
Pathophysiology
Ehlers-Danlos Syndrome, especially the vascular type, stems from defective type III collagen synthesis, leading to fragility in medium and large arteries and connective tissues.
This collagen deficiency mechanistically causes vessel wall weakening, resulting in aneurysms, dissections, and ectasias as imaging manifestations of progressive dilation and rupture risk.
In musculoskeletal structures, reduced collagen integrity produces joint hypermobility and ligamentous laxity, visualized as abnormal widening of joint spaces or subluxations on MRI, with evolution over time showing worsening instability without intervention.
Pathological processes like arterial tortuosity arise from impaired elastic recoil, measurable as vessel diameter increases beyond 1.5 times normal on CT angiography, while infarcts result from embolic occlusions secondary to dissections.
Imaging pearls include early detection of subtle ectasias before rupture, with pitfalls in mistaking tortuosity for fibromuscular dysplasia due to intracranial involvement unique to Ehlers-Danlos Syndrome.
Differential Diagnosis
Fibromuscular Dysplasia mimics arterial dissections but spares intracranial arteries and shows characteristic string-of-beads appearance on CT angiography, unlike the dolichoectasia in Ehlers-Danlos Syndrome.
Marfan Syndrome presents with aortic root dilation exceeding 4.5 cm on echocardiogram or MRI, distinguished by lens dislocation and skeletal features absent in Ehlers-Danlos Syndrome.
Loeys-Dietz Syndrome features widespread aneurysms with TGF-beta pathway mutations, but imaging shows more aggressive aortic involvement and hypertelorism not typical of Ehlers-Danlos Syndrome.
Joint Hypermobility Syndrome lacks vascular catastrophes, with MRI revealing ligament laxity without arterial ectasias or dissections seen in Ehlers-Danlos Syndrome.
Imaging Protocols and Techniques
For vascular assessment in Ehlers-Danlos Syndrome, prefer noninvasive CT angiography of chest, abdomen, and pelvis with arterial phase and 1-3 mm slice thickness to detect aneurysms and dissections.
MR angiography protocols include time-of-flight sequences for head and neck, avoiding gadolinium if renal impairment, with follow-up every 6-12 months for known lesions.
Ultrasound serves as initial screening for abdominal vessels, requiring fasting for optimal visualization, with Doppler for flow abnormalities.
MRI of spine uses T1, T2, and STIR sequences in neutral and positional views to evaluate craniovertebral instability, measuring posterior atlanto-dental interval greater than 14 mm as a red flag.
Avoid conventional angiography due to rupture risk; use echocardiogram for cardiac evaluation with focus on aortic root dimensions.
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