Etiology and Presenting Signs and Symptoms of Hygromas
Hygromas are fluid collections that can occur in different anatomical locations with varying etiologies, most commonly presenting as subdural hygromas or lymphatic malformations (cystic hygromas). 1
Subdural Hygromas
Etiology
- Spontaneous Intracranial Hypotension (SIH): Commonly caused by CSF leakage through a dural defect, leaking meningeal diverticulum, or CSF-venous fistula 1
- Traumatic: Result of head trauma with tearing of arachnoid membrane allowing CSF to collect in the subdural space 2, 3
- Post-surgical: Can develop following neurosurgical procedures 2
- Downward traction on meninges: Brain sagging due to decreased CSF volume can lead to hygroma formation 1
Presenting Signs and Symptoms
- Orthostatic headache: Pain that worsens when upright and improves when lying down (characteristic of SIH-related hygromas) 1, 4
- Mental status changes: Altered consciousness without focal neurological signs in over 50% of traumatic cases 2
- Neurological deterioration: Progressive symptoms due to mass effect in some cases 3
- Brain sagging: Radiological finding associated with SIH-related hygromas 5
- Pseudo-subarachnoid hemorrhage: Radiological finding in SIH-related cases 5
- Veno-dilatation: Engorgement of venous sinuses visible on imaging 1
- Pachymeningeal enhancement: Visible on contrast-enhanced MRI 1
Diagnostic Features
- Bilateral presentation: Often bilateral in SIH cases 5
- Age distribution: SIH-related hygromas more common in younger patients (≤55 years) 5
- Imaging characteristics: Appear as hypodense collections on CT scan, may progress to chronic subdural hematomas 5, 6
- Associated findings: May show dilated epidural venous plexus, dural enhancement, and other signs of CSF leakage 1
Lymphatic Malformations (Cystic Hygromas)
Etiology
- Congenital malformation: Arise from remnants of embryonic lymphatic tissue with proliferative potential 7, 1
- Lymphatic dysplasia: Lack of communication between lymphatic system and venous drainage, particularly in the neck 1
- Chromosomal abnormalities: Associated with Turner syndrome (45,X) in 50-80% of cases and other aneuploidies 1
Presenting Signs and Symptoms
- Soft, painless mass: Typically presents as a benign, painless swelling 7
- Location: 75-80% occur in head and neck region, commonly in posterior cervical triangle 7, 1
- Age of presentation: 80-90% diagnosed under age two 7
- Growth pattern: Can transgress anatomical boundaries through sprouting growth 7
- Bleeding: May show bleeding into vesicles at the surface of skin or mucosa 1
- Hydrops fetalis: In severe prenatal cases, can lead to nonimmune hydrops fetalis 1
Associated Conditions
- Turner syndrome: Strong association with cystic hygromas of the neck 1
- Nonimmune hydrops fetalis: Lymphatic dysplasia accounts for 5-6% of NIHF cases 1
- Other chromosomal abnormalities: Can be associated with trisomies 13,18, and 21 1
Diagnostic Approach
- MRI with contrast: Gold standard for diagnosing subdural hygromas, especially to investigate SIH 4
- CT scan: Shows hypodense collections in subdural space for subdural hygromas 6
- Ultrasound: Primary modality for detecting fetal and pediatric cystic hygromas 1
- Karyotype analysis: Recommended when cystic hygromas are detected prenatally due to association with chromosomal abnormalities 1
Clinical Pearls and Pitfalls
- Terminology confusion: Cystic hygromas have historically been called "lymphangiomas," which incorrectly implies proliferative potential 1
- Misdiagnosis risk: Subdural hygromas can be mistaken for subdural hematomas on imaging 3
- Treatment approach: Small or asymptomatic subdural hygromas can be managed conservatively, while treating any underlying CSF leak is the priority for SIH-related cases 4
- Progression risk: Subdural hygromas may progress to chronic subdural hematomas if not properly managed 5
- Differential diagnosis: Important to distinguish between different types of vascular malformations and neoplasms when evaluating neck masses in children 1