Syringomyelia

# Overview
Syringomyelia is a spinal cord cavitation, which is a central dilation due to cystic degradation expands and destroyed the spinal cord. Caused by an injury, tumors or congenital malformation like hernia. The damage can Effect the brain and nerves, that leade to Bilateral loss of pain and temperature sensation in upper extremities. weakness, stiffness, hyperReflexives in lower extremities with hyposcoliosis. Each patient experiences a different combination of symptoms. These symptoms typically vary depending on the extent and, often more critically, on the location of the syrinx within the spinal cord.

# Historical Perspective
- In the 16th century, Estienne, a French anatomist, observed spinal cord cavitation for the first time.
- In 1545, Stephanus reported a case of spinal cord dilatation in one of his patients.
- In 1688, Brunner reported a liquor filled cavity with hydrocephalus in a pediatric case.
- In 1824, Olivier d'Angers coined the term syringomyelia.
- Also in 1824, Schuppel defined the fluid in the syrinx as a hydromyelia and proposed the pathogenesis as the persistence of the fetal central canal.
- In 1882, Otto von Kohler and Fredrich Schultz defined the clinical syndrome of syringomyelia.
- Between 1883 to 1891, Cleland and Hans Chiari associated syrinx formation with hyind brain herniation in what was subsequently named Chiari malformations types I to III. 
- In 1959, Gardner described the waterhammer theory for pathogenesis of syringomyelia.
- In 1972, Ball and Dyan described the cavitation of the perivascular space as the source of syrinx formation.
- In 1980, Williams described the "suck and slosh" theory of syrinx formation.
- In 1994, Oldfield describes the piston effect of Chiari I malformation resulting in syringomyelia.
- In 2003, the Cisterna magna theory aimed to harmonize the Gardner, Williams, Oldfield and Ball&Dyan theories with neural imaging findings to propose an objective proposal of the pathogenesis of syringomyelia.

# Classification
Syringomyelia may be classified in various ways according to the anatomical features of the syrinx, or according to the underlying etiology of the disease.

## By Anatomy
Syringomyelia may be classified according to the anatomical description of the lesion (syrinx) as follows:
- Communicating vs. Non-communicating:
A communicating syringomyelia is one where the syrinx is continuous from the spinal cord, across the foramen magnum and the dilatation is continuous with the fourth ventricle
A non-communicating syringomyelia is characterized by absence of the continuity across the foramen magnum. It may present as isolated syringomyelia, or as isolated syringobulbia only affecting the brainstem with cranial nerve palsies.
- A communicating syringomyelia is one where the syrinx is continuous from the spinal cord, across the foramen magnum and the dilatation is continuous with the fourth ventricle
- A non-communicating syringomyelia is characterized by absence of the continuity across the foramen magnum. It may present as isolated syringomyelia, or as isolated syringobulbia only affecting the brainstem with cranial nerve palsies.
- Intracannalicular vs. Extracannalicular:
Intracannalicular synringomyelia originates within the central canal of the spinal cord.
Extracannalicular syringomyelia originates within the spinal cord parenchyma.
- Intracannalicular synringomyelia originates within the central canal of the spinal cord.
- Extracannalicular syringomyelia originates within the spinal cord parenchyma.

## By Etiology
Syringomyelia may be classified according to the underlying etiology or associated condition as follows:
- Congenital Malformations
- Post-infectious
- Post-traumatic
- Post-inflammatory
- Neoplastic

# Pathophysiology

## Pathogenesis
The exact pathogenesis of syringomyelia remains unknown. Several theories have been postulated about the development of a syrinx in the spinal cord. The underlying mechanisms of the disease involves disruption of CNS flow, subsequent formation of a syrinx, and enlargement of the lesion to impinge on the surrounding nerve fibers resulting in a symptomatic presentation.
- Congenital craniocervical abnormalities obstructing CSF flow from the ventricles to the central canal (e.g., arnold chiari malformation, scoliosis)
- Tumor or arachnoid cyst exhibiting a mass effect on the spinal cord
- Sequelae of spinal cord trauma results in abnormal obstruction of the central canal
- Sequelae of meningitis resulting in inflammation of the spinal cord meninges
- Sequelae of inflammatory conditions such as sarcoidosis, multiple sclerosis, seronegative spondyloarthropathies
- Gardner's hydrodynamic theory: Blockage of the foramen of Magendie at the obex results in a pulsatile "water-hammer" effect of the mass lesion on the spinal cord CSF. This pressure differential results in extravasation of fluid into the perivascular and extracellular spaces.
- William's theory: Increased intracranial pressure combined with decreased subarachnoid spinal pressure results in a "vaccuum-like" effect which further herniates the cerebellar tonsils through the foramen magnum. This results in sloshing of the subarachnoid CSF and causes extravasation of the CSF into the spinal cord parenchyma, thus creating a syrinx.
- Ball & Dyan theory: With the CSF pressure difference created by the lesion, fluid moves, collects, and expands within Robin Virchow's perivascular space.
- Oldfield's theory: The pulsatile waves of the CSF which occur during systole result in increased ICP. This increased pressure herniates the cerebellum to obstruct the subarachnoid space at the level of the foramen magnum. This pulsatile fluid wave against the surface of the spinal cord results in extravasation of fluid into the parenchyma and creates a syrinx.
- Cisterna Magna theory: This theory claims that the fluid storage capacity of the cisterna magna is the primary shock absorber of the CNS that allows the spinal cord parenchyma to remain protected from increases in intracranial pressure. Mass effect of any lesion "stiffens" the cisterna magna and results in decreased compliance of the space and increased transferrance of pressure to the spinal cord. This results in extravasation of fluid to the spinal cord parenchyma.

## Genetics
There is no genetic predilection for the development of syringomyelia. However, Chiari malformations which are the primary cause of syringomyelia have demonstrated a strong familial and genomic association.

# Causes
The most common cause of syringomyelia is Chiari I malformation. Other causes of syringomyelia may include:

## Common Causes
- Other congenital abnormalities (e.g., scoliosis, Chiari I and II malformations)
- Traumatic spinal cord injury

## Less Common Causes
- Infections (e.g., meningitis/arachnoiditis)
- Mass lesions or neoplasia (e.g., Ependymoma, hemangioblastoma, meningioma, or arachnoid cyst)
- Inflammatory conditions (e.g. multiple sclerosis, transverse myelitis, amyotrophic lateral sclerosis, sarcoidosis, other myelitis)
- Idiopathic 

# Differentiating Syringomyelia from other diseases
Syringomyelia must be differentiated from other diseases which cause gait abnormalities, sensory and motor deficit, chronic pain syndromes, urinary and fecal incontinence, and cranial nerve palsies such as:
- Normopressure hydrocephalus
- ALS
- Meningitis
- Transverse Myelitis
- Cerebrovascular accidents
- Brain tumor
- Peripheral neuropathy
- Fibromyalgia
- Parkinsonism
- Cerebellar ataxia
- Multiple sclerosis
- Neurogenic bladder
- Spinal cord space occupying lesion (e.g., tumors, cysts, abscesses)
- Guillian Barre
- Chronic demyelinating polyneuropathy

# Risk Factors
The main risk factors associated with the development of syringomyelia are based on the underlying causes:
- Congenital Malformations: Chiari malformations, Klippel Feil syndrome, congenital scoliosis
- Post-infectious: Development of arachnoiditis and development of dural abscess.
- Post-traumatic: Increasing age at time of trauma , cervical and thoracic injuries compared with lumbar, displaced fractures, and spinal instrumentation without decompression.
- Post-inflammatory: Multiple sclerosis, neurosarcoidosis, Amyotrophic Lateral Sclerosis (ALS)
- Neoplastic: Ependymoma and hemangioblastoma are most strongly associated with development of syringomyelia.

# Screening
There is no recommended screening for syringomyelia.

# Epidemiology and Demographics

## Incidence
- More than 25% of patients with spinal cord injury progress to develop syringomyelia.

## Prevalence
Syringomyelia has a prevalence estimated at 8.4 cases per 100,000 people, or about 21,000 Americans, with symptoms usually beginning in young adulthood.

# Natural History, Complications, and Prognosis

## Natural History
The essential Course of disease in Syringomyelia is temperamental. Without treatment, syringomyelia may progress to develop the worsening of neurological deficit in cases of obstructive lesions. However, the disease has a slower progression in cases of mild disease.

## Complications
Complications that can develop as a result of syringomyelia are:
- Complex regional pain syndrome
- Scoliosis
- Diaphragmatic paralysis
- Spastic ataxia
- Obsturctive sleep apnea
- Central respiratory failure
- Horner's syndrome
- Skin ulceration
- Raynaud's syndrome
- Hemihypertrophy
- Upper motor neurone lesion
- Lower motor neurone lesion
- Charcot's joints
- Raynaud's phenomenon

## Prognosis
The prognosis of syringomyelia varies depending on factors such as cause, extent of neurological damage, presence of complications, and general health status of patient before undergoing surgical treatment.
- Patients with mild neurological deficit may respond better to surgical management.
- Early management of syringomyelia in cases of trauma is associated with decreased morbidity.
- The symptoms of 80% of patients usually end due to their response to surgical treatment, as well a mild cure.
- 20% of patients gets worse despite treatment in cases of advanced disease.
- Recurrence is not uncommon in syringomyelia.

# History and Symptoms
Specific areas of focus when obtaining the history such as onset, duration and progression of symptoms; history of trauma; associated conditions like multiple sclerosis, transverse myelitis, amyotrophic lateral sclerosis, sarcoidosis, congenital malformation, infection such as meningitis or neoplasia (ependymoma, meningioma, hemangioblastoma) may help diagnosing syringomyelia. Symptoms depends on the anatomical site of spinal cord involved.

# Physical Examination
The following includes how syringomyelia might be revealed :

# Imaging Findings
Imaging studies that may help diagnose syringomyelia, its cause and complications include:

## MRI
Spinal MRI may help to diagnose and follow up syringomyelia. It is characterized by the following findings:
- Presence of syrinx in the spinal cord, its extent, location and complications
- Enlargement of central canal of spinal cord
- Presence of syrinx in the brain stem (syringobulbia)
- Presence of assocaited congenital anomalies such as chiari malformation, klippel feil syndrome, spina bifida, tethered cord syndrome
- Presence of tumors such as ependymoma
- May be used for follow up post surgery

## CT
Syringomyelia may be diagnosed as an incidental finding on CT scan. However, delayed CT scan may have a diagnostic importance in early cases of syringomyelia without clinical manifestaions. Metrizimed CT scan using non-ionic contrast may be used to identify a syrinx in postinflammatory conditions (postinfectious and posthemorrhagic arachnoiditis). In addition, computed axial tomography (CT) scans of a patient's head may reveal the presence of tumors and other abnormalities such as hydrocephalus.

## X ray
There are no specific X ray findings associated with syringomyelia.

## Myelogram
Myelogram is rarely used to diagnose syringomyelia. It uses a contrast material combined with x ray or CT to image spinal cord in case of syringomyelia. However, CT metrimised myelography is more sensitive to diagnose syringomyelia as compared to conventional myelography.

# Other Diagnostic Studies

## Electromyography
EMG findings of syringomyelia include increased excitability of spinal motor neurons. However, the findings are non specific and does not hold diagnostic importance in case of syringomyelia.

## Lumbar Puncture
Role of lumbar puncture in syringomyelia is controversial since it may result in herniation in cases of Chiari malformation. However, it may be used by some clinicians as a diagnostic tool to look for CSF pressure and signs of inflammation based on individual patient assessment.

# Medical Therapy
Drugs have no curative value as a treatment for syringomyelia. The role of medical therapy in management of syringomyelia is for treatment of underlying conditions or management of associated symptoms.

## Treatment of Underlying Conditions
Radiation and chemotherapy may be utilized for management of an underlying spinal cord tumor. 
Antibiotics may be used to treat an underlying infection (meningitis or encephalitis).

## Management of Symptoms
- Analgesics may be used to control pain.
- GABA inhibitors neurontin pregebalin may be used to control peripheral neuropathy.
- Drugs may be used for urinary or fecal incontinence or neurogenic bladder (e.g., oxybutynin, prazosin, loperamide, atropine)
In the absence of symptoms, syringomyelia is usually not treated. In addition, a physician may recommend not treating the condition in patients of advanced age or in cases where there is no progression of symptoms. Whether treated or not, many patients will be told to avoid activities that involve straining.

# Surgery
Surgery is not always required for syringomyelia. Indications for surgical management of syringomyelia include the following:
- Progressive neurological deterioration and worsening of symptoms
- Presence of tumor causing obstruction
- Congenital malformation(Chiari malformation)
- Traumatic injury to spinal cord
Surgical options used to treat syringomyelia include:

## Posterior fossa decompression
- Usually performed in Chiari malformation patients to expand the size of the posterior fossa and reverse tonsillar herniation resulting in relief of the obstructive lesion.
- This procedure may be combined with shunt, creating a large subarachanoid cistern to drain the syrinx or in conjunction with duroplasty in which dura is opened after bony removal of posterior occiput and posterior arch of C1 vertebra and a graft is sewed to dura effectively creating extra space in posterior fossa.
- Another procedure used along with posterior fossa decompression and duraplasty to help relieve obstruction is tonsillar resection or shrinkage.

## Shunt formation
Shunts are placed in order to drain the syrinx and alleviate symptoms such as headache and chronic pain syndromes. The choice of shunt is determined by the neurosurgeon; however, the following types of shunts may be performed:
Ventriculoperitoneal shunt
- Performed in patients with communicating syrinxes with hydrocephalus due to increased ventricular pressure.
- This surgery is more commonly associated with Chiari II malformations
Syringosubarachnoid shunt
- Performed more commonly in non-communicating syrinxes and is effective in rapidly reducing the size of the syrinx.
- This shunt drains the syrinx into the subarachnoid space, and the CSF is subsequently reabsorbed by the arachnoid villi.
Syringoperitoneal shunt
- Drainage of syrinx into the peritoneal cavity.

## Removal of obstruction
- In cases of tumors or arachnoid cysts as the underlying cause of the obstructive precursor lesion to syrinx formation, removal of said mass lesion may reverse the symptoms and reduce syrinx size.

## Surgical untethering and expansive duraplasty
- Performed in post-traumatic syringomyelia.
- This procedure involves establishing access to the spinal cord at the level of the injury, laminectomy, lysis of adhesions, entry into spinal cord at the site of syrinx and drainage of the syrinx into said space.
- Duroplasty is usually performed following this procedure, for regional structural support.

## Neuroendoscopic surgery
- Novel endoscopic procedure used for chiari malformation and syrinx drainage
- Minimally invasive
- Fast recovery
- Fewer complications

# Prevention

## Primary Prevention
There are no primary preventive measures associated with syringomyelia.

## Secondary Prevention
- Physiotherapy
- Prompt Surgery