RATHKE CLEFT CYSTS

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RATHKE CLEFT CYSTS

• H. ZAGHOUANI, N. EZZAIRI, A.BEN ABDALLAH,S.
  YAHYAOUI, S. MAJDOUB,T. RZIGUA, L. BEN CHRIFA,H.
  AMARA, D. BEKIR, CH. KRAIEM
• Departement of radiology, Hospital of Farhat
  Hached, Sousse, Tunisia

NR37
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INTRODUCTION

• Rathkes cleft cysts (RCCs) are benign
  congenital, non-neoplastic sellar and/ or
  suprasellar lesions originating from epithelial
  remnants of Rathkes pouch .
• These cysts are extremely common, found during
  routine autopsies in 13 to 22 of normal
  pituitaries.

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• In 1913, Goldzieher described the first case of
  RCC as an incidental postmortem finding.
• The description of RCC has expanded since the
  advent of computed tomography (CT) scanning and
  magnetic resonance imaging (MRI), showing that
  the incidence of this disease wich discovery was
  only by autopsy, was underestimated.

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OBJECTIVES

• The aim of this work is to emphasize the value
  of MRI in the positive and differential diagnosis
  of this disease through a retrospective study of
  5 cases of Rathkes cleft cyst with a literature
  review.

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MATERIALS AND METHODS

• We retrospectively analyzed the records of five
  patients with Rathkes cleft cysts collected in
  the service of radiology in the hospital of
  Farhat Hached Sousse.
•  A brain MRI was performed for all patients. All
  the cysts were discovered incidentally. 

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• There were two female and three male patients
  ranging in age from 14 to 48 years.
• MR examinations were performed using 1.5-T
  imagers.
• Axial and coronal T1-weighted images were
  obtained without administration of gadolinium.
• With axial and coronal FSE T2-weighted images.
• Section thickness was 4 mm, with intersection
  spacing of 0.

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RESULTS

• The signal, shape, size, seat and reports of the
  lesions were analyzed.
•  It showed in all cases a cystic formation of the
  sellar region with variable signals and sizes. 
• The localization of the cysts was strictly
  intrasellar in 4 cases and extended to the
  suprasellar region in one case.
•  Of the five MR scans reviewed, the lesions were
  of low signal intensity in T1-weighted images,
  there was no enhancement in post-gadolinium
  sequences .They were recorded to be of high
  intensity T2-weighted images.

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Coronal T2 MR image
Coronal T1 enhanced MR
image
Sagittal T1 MR image
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Coronal T2 MR image
Coronal T1 MR image
Coronal postcontrast T1
MR image
Sagittal post contrast T1-weighted
MR image
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EPIDEMIOLOGY

• Rathkes cleft cyst (RCC) was first incidentally
  reported by Lushka in 1860 as an epithelial area
  in the capsule of the human hypophysis resembling
  oral mucosa.
• The first symptomatic RCC case was described by
  Goldzieher in 1913.

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• RCCs have been referred to by a variety of names
  including pituitary cyst, mucoid epithelial cyst,
  intrasellar epithelial cyst, Rathkes pouch cyst,
  and colloid cyst of the pituitary.
• Not until 1934 did Frazier and Alpers propose
  its contemporary name of tumor of Rathkes cleft.

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PATHOPHYSIOLOGY

• As Voelker and colleagues have stated, the most
  common theory about the origin of RCCs is that
  the cysts are derived from true remnants of the
  embryologic Rathke pouch.
• On or about the 24th day of embryonic life, the
  Rathke pouch arises as a dorsal diverticulum from
  the stomodeum it is lined with epithelial cells
  of ectodermal origin.

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• At approximately the same time, the infundibulum
  forms as a downgrowth of the neuroepithelium from
  the diencephalon.
• By the fifth week, the Rathke pouch comes into
  contact with the infundibulum, and the neck of
  the pouch becomes occluded at the buccopharyngeal
  junction.
• During the sixth week, the Rathke pouch separates
  from the oral epithelium. Subsequently, the pars
  distalis of the pituitary gland develops from the
  anterior wall of the pouch.

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• The posterior wall does not proliferate and
  remains as the poorly defined pars intermedia.
• The residual lumen of the pouch is reduced to a
  narrow Rathke cleft, which generally regresses.
  The persistence and enlargement of this cleft is
  considered to be the cause of the RCC.
• Other authors have different theories regarding
  the formation of RCCs, suggesting instead that
  the cells of origin are derived from the
  neuroepithelium or the endoderm, or that they
  come from metaplastic anterior pituitary cells.

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ANATOMO- PATHOLOGIC FINDINGS

• Rathke cleft cysts are smoothly marginated cysts
  that vary in size from a few millimeters to 12
  cm.
• The contents vary from clear CSF-like ?uid to
  thick mucoid material.
• Microscopically, they are similar to other
  endodermal cysts (neurenteric and colloid). They
  are lined by pseudostrati?ed or single-layered
  columnar or cuboidal epithelium.

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• Cilia and scattered mucin-secreting goblet cells
  are common. Many cysts have squamous
  differentiation, and corni?ed squamous pearls are
  occasionally identi?ed.
• The intracystic nodule consists of mucinous
  material at histologic examination. Biochemical
  analysis of this material is consistent with
  cholesterol and protein.

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• Forty percent are completely intrasellar, while
  60 have some suprasellar extension through the
  cleft of the diaphragma sella .
• Completely suprasellar cysts are rare .

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PRESENTATION

• RCCs often produce no symptoms and so are usually
  discovered incidentally, when radiographic or
  necropsy findings are reviewed.
• Symptomatic RCCs are uncommon, but cysts can
  enlarge and cause symptoms secondary to
  compression of the pituitary gland, pituitary
  stalk, optic chiasm, or hypothalamus.
• Symptomatic RCCs vary in presentation headache,
  visual and/or endocrine disturbance.

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PREFERRED EXAMINATION

• MRI is the modality of choice in the detection of
  RCCs. It is superior to CT scanning for
  evaluating RCC mass extension.
• Sagittal and coronal MRI scans provide reliable
  information concerning the relationship of the
  mass to the optic nerves, optic chiasm, and
  hypothalamus.

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• Coronal MRI is also helpful in the evaluation of
  the lateral extension of the sellar cyst and its
  relationship to the internal carotid arteries and
  cavernous sinuses. MRI also has superior
  multiplanar capabilities and contrast resolution
  compared with those of CT scanning.
• The advantage of CT scanning is that it is
  superior to MRI in depicting small amounts of
  calcium.

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• This advantage can be important, because the
  presence of calcification tends to indicate an
  alternative diagnosis, such as craniopharyngioma,
  although small calcifications are observed in
  some cases of RCC. CT scanning is also superior
  to MRI in the evaluation of associated bony
  remodeling.

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COMPUTED TOMOGRAPHY

• Rathke cleft cysts (RCCs) frequently appear as
  well-circumscribed, hypo-attenuating, cystic
  sellar masses that may have suprasellar
  extension.As a result of the different cystic
  contents, RCCs may appear iso-attenuating or
  hyperattenuating relative to the brain
  parenchyma.
• RCCs usually have a thin wall that may enhance.

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• Variability in CT scan contrast enhancement among
  individual cysts may reflect squamous metaplasia
  in the wall or a peripherally displaced rim of
  pituitary tissue.
• Extravasation of cystic contents may inflame
  nearby structures, resulting in enhancement.
• Calcification characteristically is not depicted
  on CT scans, although Shin and colleagues have
  described this finding in a number of
  cases.Complex cysts may have septations.
• Large cysts may cause bony remodeling.

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MR IMAGING

• The best imaging clue is a non enhancing non
  calci?ed intra- and/or suprasellar cyst with an
  intracystic nodule . While this is the typical
  picture, the imaging characteristics vary widely.
  
• Approximately half are hyperintense on T1-
  weighted images, while half are hypointense. On
  T2-weighted images, 70 are hyperintense and 30
  are iso- or hypointense.

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• Although no characteristic MRI features have been
  identified, many RCCs are in 1 of the following 2
  groups
• Rathke cleft cysts (RCCs) with low signal
  intensity on T1-weighted images and high signal
  intensity on T2-weighted images.
• RCCs with high signal intensity on T1-weighted
  images and variable signal intensity on
  T2-weighted images.
• The cystic contents of the first group resemble
  those of cerebrospinal fluid (CSF). In the second
  group, an increase in the signal on T1-weighted
  images has been

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• related to the high content of
  mucopolysaccharides, which is believed to result
  from an increase in the number of mucin-secreting
  cells in the cyst wall, as well as from an
  increase in the activity of these cells.
• Uncommon cases with high signal intensity on
  T1-weighted images and low signal intensity on
  T2-weighted images have been suggested to result
  from a combination of factors, including the
  presence of mucopolysaccharides, chronic
  hemorrhage, a high cholesterol content, and
  cellular debris from the cyst wall.

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• A small nonenhancing intracystic nodule is
  considered a virtually pathognomonic sign of a
  Rathke cleft cyst. These nodules show high signal
  intensity on T1-weighted images and low signal
  intensity on T2-weighted images, and they do not
  enhance.
• Rathke cleft cysts do not enhance after contrast
  material administration, although an enhancing
  rim of displaced compressed pituitary gland is
  present in approximately half of the cases.

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• The report's authors went on to conclude that,
  with regard to RCCs, DWI-SSFSE with apparent
  diffusion co-efficient (ADC) values provides
  objective information for differentiation from
  other sellar cysts. DWI-SSFSE with ADC values can
  also be employed in the differentiation of RCCs
  from craniopharyngiomas and hemorrhagic pituitary
  adenomas. All the RCCs are hypo-intense relative
  to the normal brain parenchyma (restricted
  diffusion) .

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DIFFERENTIAL DIAGNOSIS

• The differential diagnosis for Rathke cleft cysts
  includes craniopharyngioma, cystic pituitary
  adenoma, or other non neoplastic cysts (arachnoid
  cysts or epidermoids) .
• Unlike Rathke cleft cysts, craniopharyngiomas
  typically demonstrate calci?cation and
  approximately 90 have nodular, globular, or rim
  enhancement.

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• The presence of solid enhancing nodules in the
  cyst wall also favors the diagnosis of
  craniopharyngioma.
• The rare noncalci?ed cystic nonenhancing
  craniopharyngioma, a ?nding more common in adults
  than in children, may be impossible to
  distinguish from Rathke cleft cyst with imaging
  ?ndings alone.

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TREATMENT

• The most common approach in the treatment of RCCs
  is transsphenoidal surgery, in which the cyst is
  partially excised and drained. 
• This method is effective and helps to preserve
  pituitary function.
• Radical excision can cause additional and
  unnecessary pituitary damage therefore, it is
  not the treatment of choice.
• In transsphenoidal surgery, the cyst is opened,
  a biopsy specimen is obtained from the wall, and
  the cyst is drained into the sphenoid sinus.

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• An interesting aspect of treatment is the
  decrease in the size of the cyst after high-dose
  steroid therapy. Although the pathophysiologic
  mechanism is not clear, the steroids are assumed
  to have an effect on the secretion or absorption
  of cystic fluid. This finding suggests that
  steroid therapy may be useful in some patients
  with an RCC and inflammatory changes. Further
  study in this area is needed to gauge its
  effectiveness is the treatment of RCCs.

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CONCLUSION

• The MRI is effecticient in the positive and
  especially the differential diagnosis of these
  cysts, and to guide the therapeutic decision.Once
  the diagnosis is considered, a spaced clinical
  and MRI monitoring is adopted in cases
  of asymptomatic cyst, while a surgical
  treatment is proposed for the rare symptomatic
  cysts.
•