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Please be aware the following article contains photographs of a real operation and the photographs are enhanced for clarity.

Surgery for Chiari 1 Malformation.

Numerous surgical procedures have been proposed for the treatment of Syringomyelia associated with Chiari 1 malformation, but the optimal treatment has not yet been uniformly standardised. The main aim of the surgical treatment of Syringomyelia/Chiari complex is directed toward restoration of physiological cerebrospinal fluid dynamic at the craniocervical junction. Posterior fossa (foramen magnum) decompression utilizing suboccipital craniectomy and duraplasty remains the most commonly performed surgical treatment for Chiari-associated Syringomyelia. In the presence of basilar invagination, anterior decompression, typically transoral odontoidectomy, or posterior decompression may be performed, however the former is rarely necessary, especially as a first procedure. For posterior fossa decompression, with or without other procedures usually combined with dural patch grafting and cervical laminectomy of C1 through C2 or C3 the anaesthetised patient is positioned prone on the operating table with the head in headholder pins. The neck is flexed to open the interspace between the occiput and the posterior arch of C1. The shoulders are retracted inferiorly with adhesive tape. A midline incision from the inion to about C4 spinous process is made and the muscle and soft tissues are dissected off the occiput, C1 and C2 (if necessary) in the subperiosteal plane. Removal of the bone above the foramen magnum should be about 3cm high and 3cm wide and in most cases the posterior arch of C1 also needs to be removed.
 

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              Figure 1..

Figure 1. Suboccipital craniectomy and C1 laminectomy. The bone has been removed and the dura covering the cerebellum and upper spinal cord has been exposed: (FM = level of foramen magnum; C1 = level of C1 lamina) The dura is opened with a "Y" shaped incision and the top flap is excised. One should be aware that the transverse sinuses are usually very low in Chiari malformations. The main aim of the procedure is a cervical laminectomy and to open the foramen magnum to decompress the tonsils.
 

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                               Figure 2.

Figure 2. The same exposure as on Figure 1. following "Y" shaped incision of the dura. The cerebellar tonsils are clearly visible extending below the level of the previously removed C1 lamina. A graft of periosteum, facia lata or an allograft is sutured onto the dural opening to provide more room for the tonsils and the lower brain stem (duraplasty).Occlusive material like thrombin/fibrin tissue glue may be used to avoid cerebrospinal fluid leak although careful haemostasis and tight wound closure in layers usually is sufficient to avoid this complication. The patient is then nursed head up after reversal of the general anaesthetic.
Some surgeons would include procedures to plug the obex (bottom of 4th ventricle) with muscle or teflon, drainage of syrinx, if present, at the same procedure usually by fenestration through the dorsal root entry zone of the cord with or without stent or shunt, 4th ventricular shunting, or opening the foramen of Magendie (midline opening of the 4th ventricle), if obstructed. Some authors would attempt to remove adhesions binding the tonsils together and even shrinking the tonsils down with bipolar coagulation. Others advocate performing a transoral clivus-odontoid resection in cases of ventral brain-stem compression, as they feel these patients may potentially deteriorate with posterior fossa decompression alone. This may be reasonable to perform as a second procedure after posterior fossa decompression in cases of clinical deterioration or progression of basilar impression on serial MRI scans. However, in my view, none of the above mentioned procedures are routinely necessary during standard posterior fossa decompression 5mm descent of cerebellar tonsils from the level of the foramen magnum is often cited as the cut-off below which one may consider the tonsils low enough to qualify for a Chiari type I malformation. This can be easily determined on sagittal MRI scans. This radiological finding together with the clinical signs and symptoms would be the criteria to perform posterior fossa decompression.
 

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             Figure 3.

Figure 3. Chiari I malformation with cervical syrinx. The cerebellar tonsils extend to the lower end of C1 lamina (the same patient as on Figures 1 and 2).

SYRINGOMYELIA

Cystic cavitation of the spinal cord also known as syrinx. Based on aetiology, cell-type of lining, or presence/absence of communication with the central canal syrinx may be divided into subtypes. It may be associated with certain congenital or neoplastic conditions, or may follow significant spinal trauma with or without clinical signs of spinal cord injury. There are two main forms:

1. Communicating Syringomyelia: primary dilatation of the central canal. Almost always associated with abnormalities of the foramen magnum, e.g. Chiari I malformation or basilar arachnoiditis (post-infectious or idiopathic). Simple central canal dilatation with ependymal cell lining is called hydromyelia; extension into the cord parenchyma constitutes true Syringomyelia.
 

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                    Figure 4.

Figure 4. Extensive cervical and upper thoracic syrinx associated with Chiari I malformation (same patient as on Figures 1-3)

2. Noncommunicating Syringomyelia: cyst arises in the cord substance and does not communicate with central canal or subarachnoid space. May be due to trauma, neoplasm (mostly gliomas), or arachnoiditis. True syrinx cavities contain fluid of the same constituency as CSF, whereas tumour cyst fluid is usually highly proteinaceous.

Communicating Syringomyelia:

Aetiology probably lies in the outlet obstruction (partial or complete) of the fourth ventricle (foramina of Luschka and Magendie), as mentioned above. Congenital conditions like Chiari malformation type I or II, cerebellar ectopia, basilar impression, Dandy-Walker syndrome, and acquired conditions such as adhesive arachnoiditis are associated with high incidence of syrinx. Major theories of syrinx formation are the hydrodynamic ("water-hammer") theory of Gardner and William's theory of "hydrodissection". The former states that systolic pulsations are transmitted with each heartbeat from the intracranial cavity to the central canal and the latter assumes that manoeuvres, which raise CSF pressure (valsalva, coughing, etc.) cause "hydrodissection" through the spinal cord tissue.
The clinical syndrome is non-specific and may characterize any intramedullary spinal cord pathology. It may include sensory loss (similar to central cord syndrome) with a "cape" of dissociated sensory loss (loss of pain and temperature sensation with preserved touch and joint position sense; may result in painless ulcerations from unperceived injuries), cervical and occipital pain, lower motor neuron hand and arm weakness and painless (neurogenic) arthropathies (Charcot's joints) seen in less than 5 % of the cases.
The investigation of choice is MRI scanning in sagittal and axial planes. If for some reason MRI is not possible, CT myelography with water-soluble contrast is performed.
The first choice of surgical treatment is posterior fossa decompression when posterior anomalies (e.g. Chiari malformation) are present. Various shunting procedures may be performed if posterior fossa decompression is not warranted (no posterior anomaly present) or not successful in reducing the size of the syrinx. Shunting the fluid from the syrinx to the peritoneal, pleural or subarachnoidal spaces may be performed. Other procedures, like plugging the obex, syringostomy (opening the syrinx to the subarachnoid space without leaving a tube), and percutaneous syrinx aspiration (may be used repeatedly) are rarely indicated.
Assessing treatment outcome is difficult due to rarity of the condition, variability of natural history (which may arrest spontaneously), and too short follow-up.
Posttraumatic Syringomyelia is a form of Noncommunicating Syringomyelia. It may occur following penetrating injury or non-penetrating "violent" trauma to the spinal cord as well as a result of post-spinal anaesthesia or following thoracic disc herniation. They often present late (years or even decades after the injury) and may affect about 0.3-3 % of cord injured patients. The late appearance of upper extremity symptoms in a paraplegic or paraparetic patient should raise high index of clinical suspicion of posttraumatic Syringomyelia. Surgical management involves intradural lysis of arachnoid adhesions to the inner surface of the dura at the level of the spinal column fracture or abnormal angulation followed by expansive duraplasty and various shunting procedures of the syrinx.

Syringobulbia is the central cavitation of the medulla. It is commonly associated with a syrinx extending to involve the brain stem. The clinical features of Syringobulbia include: facial pain and dissociated sensory loss vertigo and nystagmus - VIII cranial nerve, facial palatal or laryngeal palsy - VII, IX, X, XI cranial nerves dysfunction, wasted tongue - XII cranial nerve dysfunction, Horner's syndrome - sympathetic loss

The above article was kindly donated by;
Mr. Karoly M. David FRCS (SN)
Consultant Neurosurgeon
 


The GP and Syringomyelia.

The GP has many functions, educational, diagnostic, chronic disease treatment advocacy and so on.
With a comparatively rare disease as this, he is only likely to be involved in the early stages of diagnosis, and in the long term general medical care of the person for whom Syringomyelia may be only one of several medical problems. He will fulfill his role alongside nurses, occupational therapists and so on. The definitive treatment of the condition is usually surgical and highly specialised, and it is one of the GP's jobs to access such expert help on behalf of his/her patient.
He will also be the medic who remains constant for the patient for long periods of time; specialists come and go, but changes of GP are generally initiated by the patient rather than the professional. He will also be there to provide not only help and advice about Syringomyelia, but also for any other medical problem the patient may present. Hence his relationship with the patient has a length and breadth that is special to general practice.
Syrinx, a pipe; myelos, marrow; a fair description of the way in which Syringomyelia turns the spinal cord into a tube by creating a long cavity in it. This process damages some of the nerve fibres in the spinal cord in a characteristic pattern; the ability to sense pain and temperature may be damaged while the sensing of a light touch remains intact. However the extent of disability is much broader than this, depending upon the position and size of the syrinx; the impact of this upon the patient, his life and those around him may be devastating, and every effort is made to treat the condition and to reduce its effects.
As with many rare conditions, the patient becomes highly knowledgeable about his condition, often more so than the GP. The erudite information available about this condition is to be found with the neurologist and his specialised team; there is often a nurse specialist, occupational therapist, physiotherapist and psychologist to tap for information and help with most aspects of the disease. The GP may be seen as someone independent of this, involved in and hopefully trusted with all the other aspects of a patient's health, who can act as advocate and friend in all of this. Sometimes there is little for him to do, sometimes a great deal. Above all he is there on a day to day basis; the neuroteam cannot usually be accessed at very short notice; the GP is available in that way, can help to decide if a problem needs urgent intervention or can wait, and what the urgent implications of a new symptom may be.

Many thanks to my G.P. for contributing to this Web Site.
 

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                                                                    www.chiari-info.co.uk  Last update..27-01-2010

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