Pseudomeningocele following Chiari surgery decreases quality of life

Pseudomeningocele (PM) is one of the more common complications following posterior fossa decompression for the Chiari I malformation (CM-I). A leak of spinal fluid through the duraplasty creates a pocket of CSF in the posterior cervical muscles. If the fluid collection enlarges, it pushes the duraplasty membrane into the foramen magnum region causing crowing and recurrence of the Chiari symptoms. In a few cases, spinal fluid leaks through the incision and, if untreated, leads to infection.

While a number of Chiari centers have been able to keep the risk of pseudomenigocele very low, rates as high as 18% patients have been reported.  

If the PM is small, it can be observed with follow-up MRI scans and may resolve on its own. However, large persistent PMs pose difficulties. The duraplasty can become adherent to the underlying cerebellar tonsils and block CSF flow. Once adherent, surgical revision is difficult.

Dr. Scott Parker and colleagues at the Department of Neurological Surgery at Vanderbilt University studied the effects of symptomatic PMs on the 1-year postoperative “pain, disability, and quality of life” in patients undergoing Chiari decompression.

The researchers found that “a postoperative symptomatic pseudomeningocele has lingering effects at 1 year, which significantly diminishes the overall benefit of suboccipital decompression for CM-related symptoms.”

While the authors use this finding to argue for a “less invasive approach,” I have a different view. The less invasive approaches, such as thinning of the dura by stripping its outer layer, have a higher a risk of failure than the duraplasty approach.

The goal of surgery for the Chiari malformation is adequate posterior fossa decompression with minimal surgical risks. Thus, the key is to use a duraplasty technique that markedly decreases the risk of pseudomeningocele. This is possible through the use of autologous pericranium harvested from a separate small incision in the midline occiput just above the main incision.

Using triangular silastic templates, the appropriate size of graft can be obtained. The pericranial graft is sutured in place with a monofilament running suture in a watertight fashion. Two Valsalva maneuvers to 35 cm are performed following the repair and if any leak is visualized under microscopic magnification, the area is oversewn or a secondary patch is used.

Durplasty using a patient’s own pericranial tissue has been effective in posterior fossa decompression for patients with CM-I. The leak rate can be reduced to a minimal level: 2% or less. The use of a duraplasty results in greater expansion of the subarachnoid space at the foramen magnum than possible in non-duraplasty procedures and allows the patient the best opportunity to improve.

If a leak does develop, it is followed closely and if it enlarges, treated with lumbar drainage or surgical revision. Fortunately, the likelihood is low in centers experienced with the pericranial duraplasty technique.

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Effect of symptomatic pseudomeningocele on improvement in pain, disability, and quality of life following suboccipital decompression for adult Chiari malformation Type I

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Another Reason to Evaluate the Foramen of Magendie during Posterior Fossa Decompression for Chiari-related Syringomyelia

Image from the Editor's files shows the median aperture of the 4th ventricle, also known as the foramen of Magendie, covered by a veil in this person with Chiari & syringomyelia. Image: CyberMed, LLC

Image from the Editor's files shows the median aperture of the 4th ventricle, also known as the foramen of Magendie, covered by a veil in this person with Chiari & syringomyelia. Image: CyberMed, LLC

When treating a patient with Chiari related syringomyelia by posterior fossa decompression, it is important for the neurosurgeon to open the dura and the arachnoid and evaluate the outlet of the fourth ventricle which drains CSF into the cisterna magna. The outlet called the foramen of Magendie after its discoverer is also known as the median aperture. Approximately 1 of 10 persons with Chiari/syringomyelia has a veil over the median aperture blocking or restricting CSF flow. Clearing the obstruction by microsurgically opening the veil facilitates syrinx decompression and helps avoid revision surgery.

In the December 2014 issue of the Journal of Neurosurgery, S. Grossaur of the Department of Neurosurgery, General Hospital of Klagenfurt, in Austria, and colleagues Koeck K, Vince GH published a report documenting significant improvement in the somatosensory evoked potentials (SSEPs) following the opening of an obstructed foramen of Mangendie. The authors describe the

case of a 32-year-old woman who underwent surgery for CM associated with extensive cervicothoracic syringomyelia and whose intraoperative somatosensory evoked potentials (SSEPs) did not notably improve after craniotomy or following durotomy; rather, they only improved after opening of the fourth ventricle and restoration of CSF flow through the foramen of Magendie. Postoperatively, the patient recovered completely from her preoperative neurological deficits. To the authors' knowledge, this is the first report of significant SSEP recovery after opening the fourth ventricle in the decompression of a CM-I.

When evaluating patients referred for persistent syringomyelia following posterior fossa decompression, who on MRI studies appear to have an adequate decompression, a careful review of the operative note should be performed to determine if the dura and arachnoid where opened during the initial procedure. If the dura or arachnoid had not been opened, the revision surgeon should consider exploration of the posterior fossa and examination for a possible median aperture veil (retained rhombic roof) as the preferred treatment strategy instead of placement of a syrinx stent or shunt. 

John Oró, MD
January 2, 2015

Theodor Langhans described the Chiari I malformation in 1881

Dr. Theodor Langhans, Professor and Chair of Pathological Anatomy in University of Bern, Switzerland.

Dr. Theodor Langhans, Professor and Chair of Pathological Anatomy in University of Bern, Switzerland.

Hans Chiari is appropriately recognized for describing and categorizing the Chiari malformations in reports published in 1891 and 1895. While others such as Jean Cruveilhier (1798-1874) and John Cleland (1835-1925) also made observations prior to Chiari, in an article published in the Journal of Neurosurgery: Pediatrics in March 2011 Martin M. Mortazavi and colleagues propose Theodor Langhans, the German pathologist remembered for describing “Langhans cells” in tuberculosis, as the first to describe the Chiari I malformation.

Mortazavi et al. review Theodor Langhans’ distinguished background:

“Theodor Langhans was born September 28, 1839, in Usingen (Nassau), Germany, and studied under Henle in Göttingen and von Recklinghausen in Berlin. He attended medical school in Heidelberg and, in 1864, completed his medical degree thesis on the structure of tendons in Würzburg. He was also a student under such names as Virchow, Trauber, and Frerichs. He served as assistant to von Recklinghausen until 1867. In Marburg, he collaborated with Lieberkölin and Wagner on anatomical research. He was later made Professor Ordinarius in Giessen and then moved to Switzerland in 1872 where he was appointed Professor and Chair of Pathological Anatomy in Bern, succeeding Klebs.”

In 1881, Langhans described a case of syringomyelia and “pyramidal tumors” of the cerebellum in the publication Über Höhlenbildung im Rückenmark als Folge Blutstauung. Mortazavi et al. translated the report (“Regarding cavity creation in the spinal cord as a consequence of obstruction to blood flow”) and believe “these were the first descriptions of what would become known as the Chiari I malformation described by Langhans as ‘pyramidal tumors.’” These selected passages are key to the description and reveal Langhans awareness of the anatomy and pathophysiology of CMI:

“In the case, which first brought to my attention the necessity to look for cavity formation in the spinal cord following a change in the cerebellar cavity, I could not find a cause for the increase in pressure; but great pressure on the pons and medulla oblongata from above was indeed apparent. Upon dissection of the cerebellum, nothing was of note except for an obvious/significant development of both tonsils, which protruded down in the form of two symmetrical pyramidal tumors and pushed the medulla oblongata in a frontal direction at almost a right angle.” (emphasis added)
“The increase in pressure in the cerebellar cavity will hinder or greatly impede the outflow of blood and cerebral spinal fluid.” (emphasis added)

Mortazavi and colleagues recognize Langhans' contribution and conclude:

“Although the association of Chiari I malformation and syringomyelia would not be commonly used until the late 20th century, it was Langhans in the 19th century who proposed this cause and effect. Therefore, appropriate recognition for this association should be given to this early pioneer who, with Chiari, helped provide us with details of hindbrain herniation that are still in use today.” 

John Oró, MD



The first description of Chiari I malformation with intuitive correlation between tonsillar ectopia and syringomyelia: Historical vignette

Martin M. Mortazavi, M.D., R. Shane Tubbs, M.S., P.A.-C., Ph.D., Maja Andrea Brockerhoff, M.A., Marios Loukas, M.D., Ph.D., and W. Jerry Oakes, M.D.

Pseudotumor cerebri a major factor in failure following surgery for the Chiari I malformation

Improving treatment outcome in the Chiari I malformation (CM1) depends on many factors; among the most important is the recognition of associated co-morbidities. A common associated condition is idiopathic intracranial hypertension, also known as pseudotumor cerebri (PTC).

In 2006, Fagan et al. of The University of Chicago Children’s Hospital in Chicago, Illinois published a milestone study recognizing the importance of considering this disorder in patients with CM1, especially as the body mass index of the U.S. population continues to increase.

The authors defined the problem and goal of their study –

“The etiology of Chiari malformation type I (CM1) as well as other anomalies associated with CM1 remains poorly defined. We have noted the presence of elevated CSF pressures with small ventricles, consistent with the pseudotumor cerebri (PTC) syndrome in a group of CM1 patients that did not respond over the long term to posterior fossa decompression. In order to better understand this association, we reviewed a series of CM1 patients treated by posterior fossa decompression to define the prevalence and nature of post-Chiari PTC.”

The records of 192 patients with CMI previously treated by posterior fossa decompression were reviewed. The 36 patients failing surgery had a lumbar puncture performed to measure their spinal fluid pressure. Of these, 15 patients (42%) were found to have elevated intracranial pressure consistent with pseudotumor cerebri; a high number that should serve to get this disorder on the radar of all healthcare providers caring with persons with CM1.

Of the 15 patients found to have the Chiari pseudotumor cerebri syndrome, 14 required subsequent treatment with a CSF shunt. Outcome following shunt placement varied depending on age of the patient: “Seven of 9 pediatric patients had significant symptom resolution while 6/6 adult patients remained variably symptomatic.”

The author’s concluded:  

“CM1 and PTC co-exist in a surprising percentage of failed operative CM1 patients and present with a syndrome that is difficult to treat.” (emphasis added)

Future posts will look further at this important syndrome including its presentation, diagnosis and treatment.


Fagan LH, Ferguson S, Yassari R, Frim DM.
The Chiari pseudotumor cerebri syndrome: symptom recurrence after decompressive surgery for Chiari malformation type I
Pediatr Neurosurg. 2006;42(1):14-9

Blood glucose, memory and dementia

Currently at the Las Vegas airport waiting for my return flight to Denver. This morning I attended the Chiari & Syringomyelia Foundation public meeting at the University of Nevada, Las Vegas. A section of my talk was on the Chiari/Pseudotumor Cerebri Syndrome, a challenging condition in which the Chiari I malformation and pseudotumor cerebri occur together.

In 2006, Dr. David Frim and colleagues at The University of Chicago described the syndrome in a study of 36 patients that had failed Chiari surgery. The study revealed 42% of these patients had associated pseudotumor cerebri (AKA: idiopathic intracranial hypertension), a condition of raised brain pressure of uncertain cause. 

Since one of the suspected causes of pseudotumor cerebri is inflammation, a question at the end of the presentation led to a discussion of the role of nutrition. While inflammation is a complex and not yet fully understood condition, information is developing on the neurological effects of sugar in our diet.  I mentioned two recent studies warning us that even mild elevation of blood glucose (above normal but not to the diabetic level) can hurt the brain.

One study showed that mildly elevated blood glucose can shrink the hippocampus, the key brain center for memory storage. The other study revealed mildly elevated blood glucose increases the risk of dementia. To learn more about these two studies, see my posts on