spinale Arachnoidalzyste

Zufallsbefund
einer lateralen meningealen Zyste auf Höhe BWK 12. (MRT wegen LWK-4-Fraktur). Die Zyste findet sich auf Höhe des Wirbelkörpers im Gegensatz zu einer Wurzeltaschenzyste, die sich in die Foramina ausdehnt und diese ggf. aufweitet. Die in T2 signalreichere Darstellung ggü. dem Liquor im Duralsack ist durch Pulsationen in letzterem erklärt.
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Dorsal
arachnoid web: the ‘scalpel’ sign—a case report and differential diagnosis. MRI of the arachnoid cyst in dorsal spine T2W sagittal (a) and axial (b, c) sections demonstrating an increase in the posterior arachnoid space in mid and lower dorsal spine displacing and compressing the spinal cord anteriorly. A thin membrane is observed at the upper end (white arrow in a) and anterior edge (white arrows in c)
ejrnm.springeropen.com • CC-by-4.0
Spinal
arachnoid cyst secondary to meningeal metastasis. T1 sagittal image cervical and thoracic spine. Arachnoid cyst seen at T 7 level tethering the cord posteriorly. Multiple compression fracture is also seen.
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Ventral
cervical spinal intradural arachnoid cyst: an unusual presentation. Spinal MRI in the axial plane demonstrates how the spinal cord (red arrows) is displaced to the right and compressed by the intradural lesion already described (yellow arrows).
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Ventral
cervical spinal intradural arachnoid cyst: an unusual presentation. Spinal MRI in the sagittal plane shows an extramedular lesion (yellow arrows), anterior to the spinal cord, that is hypointense in T1WI, hyperintense in T2WI and showed no enhancement after endovenous contrast administration.
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Surgical
outcome of primary intradural spinal arachnoid cysts: a series of 10 cases. Case 1: 3-year-old male child presented by delayed motor milestones; clinical examination revealed quadriparesis. Preoperative MRI (a) sagittal T2 and (b) axial T2 showing ventral cervicothoracic spinal arachnoid cyst compressing the cord and pushing it posteriorly. The patient was operated for laminoplasty and cyst wall marsupialization. Follow-up MRI 3 months later (c) sagittal T2 and (d) axial T2 showing cord decompression and return to original position. The patient was clinically and radiologically stable during annual follow-up
ejnpn.springeropen.com • CC-by-4.0
Spinal
arachnoid cyst secondary to meningeal metastasis. T2 sagittal images cervical and thoracic spine with zoomed-in area of lower cord showing abnormal signals.
www.eurorad.org • CC by-nc-sa-4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

Spinal arachnoid cysts are relatively uncommon and may be either intradural (type III meningeal cyst) or extradural (type IA meningeal cyst).

This article specifically focuses on spinal arachnoid cysts. For a general discussion of arachnoid cysts, refer to the main article: arachnoid cyst.

Epidemiology

Spinal arachnoid cysts may present at any age. There is no gender predilection.

Clinical presentation

Most spinal arachnoid cysts are asymptomatic and are discovered incidentally. Clinical symptoms, if present, may include progressive spastic or flaccid paralysis, pain, weakness, numbness, and/or bladder/bowel incontinence. Symptoms may be exacerbated by postural changes and the Valsalva maneuver .

Pathology

As with any arachnoid cyst, spinal arachnoid cysts are CSF-filled sacs contained by the arachnoid mater. The degree of communication with the surrounding CSF space is variable with some cysts freely communicating and others not at all .

Etiology

They may be congenital or acquired. Secondary arachnoid cysts are usually due to trauma, hemorrhage, inflammation, surgery or iatrogenic injury like lumbar puncture, injection of anesthetic or contrast material within the subarachnoid space .

Location

Most primary intradural spinal arachnoid cysts are dorsal to the cord. They occur at the following locations:

  • thoracic: 80%
  • cervical: 15%
  • lumbar: 5%

Secondary spinal arachnoid cysts can be located anywhere, depending on where the insult has occurred (see "Etiology" above).

Associations

Radiographic features

CT

On CT myelography, the compressed cord is displaced anteriorly . Most arachnoid cysts eventually opacify with contrast, although the rate at which they do so is variable . In many instances, the cyst opacifies readily and as such, it may be challenging to diagnose with certainty. Early scanning is advisable, to 'catch' the cyst before it becomes isodense to CSF while considering the need for more delayed scanning if appropriate CSF mixing is not achieved. This may necessitate the introduction of contrast on the CT table rather than at fluoroscopy.

MRI

As the cysts follow the intensity of CSF and their walls are generally not visible, they may not be identified unless the cord is displaced.

  • T1: CSF intensity
  • T2: CSF intensity, may even be brighter than CSF since there is no signal loss from pulsation/flow
  • T1 C+ (Gd): no contrast enhancement
  • phase-contrast imaging: decreased CSF flow within the cyst
  • DWI: no evidence of restricted diffusion

Treatment and prognosis

Incidental asymptomatic cysts are managed conservatively. Symptomatic cysts can be treated with surgical excision. An important component of surgical treatment of epidural cysts includes closure of the arachnoid defect, if any, which could become a source of CSF leak.

Differential diagnosis

For intradural arachnoid cysts, several alternative diagnoses should be considered:

  • herniated ventral cord
    • focal cord deformity
    • phase-contrast MRI: absence of CSF flow ventral to the herniated cord and a normal CSF flow pattern dorsal to the cord
    • can be challenging to distinguish; myelography may be helpful
  • spinal epidermoid cyst
    • bright on DWI (as in the brain, spinal epidermoids are differentiated from arachnoid cysts by their brightness on DWI)
  • spinal dermoid cyst
    • most common location is the lumbar spine
    • imaging characteristics are variable but usually resemble fat
  • spinal endodermal cyst:
    • common in the lower cervical and upper dorsal spine ventrally
    • usually Indistinguishable from an arachnoid cyst on imaging
  • spinal hydatid cyst
    • most commonly extradural (intradural extramedullary lesions are extremely rare)
    • usually multiloculated
    • may show minimal enhancement
  • spinal cysticercosis
    • peripheral enhancement
    • usually multiloculated

Rarely, extradural cysts may be considered, although they are generally clearly not within the dura. They include:

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu spinale Arachnoidalzyste:
Arachnoidalzyste
 
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Synovialzyste
 
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Wurzeltaschenzysten
 
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intraspinale
zystische Läsionen
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