Saturday 28 December 2013

Focal Adhesive Arachnoiditis of Spinal Cord

A 35 y o male with both lower limb weakness.
History of meningitis in the past ~10 years back.
History of major trauma ~7 years back. 

MRI whole spine with contrast
This MRI study of whole spine with contrast shows:
Multiple loculation in the the Csf space anterior to cord in dorsal region iso intense to Csf. 
Changes of myelomalacia with cavitations.
No abnormal cord or lepto meningeal enhancement on post contrast. 
Lower cord and conus spared, Conus pulled up owing to upward traction. 
Multiple rib fractures on either side. 
Cauda equina normal. 

Imaging diagnosis: Focal Adhesive Arachnoiditis of the Spinal Cord with Myelomalacia. 

Focal Adhesive Arachnoiditis of the Spinal Cord

Adhesive arachnoiditis may result in the formation of syringomyelia or myelomalacia, causing neurological deterioration such as sensory disturbances in the extremities, urinary disturbance, or sexual dysfunction.
Basic studies suggest that spinal tissue scarring at the injury site may cause a tethering effect on the spinal cord, which may lead to significant alterations in CSF dynamics. It is speculated that the rostro caudal CSF pulse wave is misdirected into the spinal cord parenchyma. The resulting high intramural pressure and decreased compliance of the subarachnoid space favor the flow of fluid into the spinal cord, possibly through perivascular spaces, resulting in a destructive cavitation process and eventually the formation of a syrinx cavity.
Causes of Adhesive arachnoiditis include hemorrhage, infection, trauma, radiation necrosis, ischemic infarction, or surgery.

Adhesive Arachnoiditis and Foix-Alajouanine Syndrome 

Modern understanding of the non-infectious neuropathologic entity "adhesive arachnoiditis" began in 1926 with the publication "La Myélite nécrotique subaiguë (Myélite central angiohypertrophique évolution progressive) Paraplégie amyotrophique lentement ascendan d'abord spasmodique, puis flasque"  by authors C. Foix and T. Alajounanine in the French Revue Neurologique (Paris), 2: 1-42).

What these authors described were cases which, in all probability, represented primary spinal cord Arterio Venous malformations producing recurrent subarachnoid hemorrhage.  A-V malformations represent congenital abnormalities of blood vessel development.  They are collections of abnormal and flimsy blood vessels which shunt blood directly from arteries to veins. Because these blood vessels are so fragile they are likely to spontaneously bleed on an intermittent basis.

The subarachnoid space represents the "salum sanctorum" of the human body.  It abhors all foreign body substances.  Even the presence of injected air is considered to be a "foreign body."  Blood is definitely considered a foreign body (particularly the breakdown products of blood ).  Repeat exposure to foreign body substances in the subarachnoid space can initiate auto-immune amnestic reactions which may potentiate and magnify the ongoing inflammatory process leading to severe local arachnoid fibrosis, associated thrombosis of local blood vessels, progressive destruction of the spinal cord producing myelomalacia and cystic degenerations in cord.

Initially the Foix-Alajouanine pathologic entity was only an autopsy phenomenon until the advent of high resolution MRI and associated modern spinal angiography.  This entity was mainly a medical curiosity until the midpart of the 20th century when some clinicians took a special interest in this entity. David B. Clark, neurologist at the Johns Hopkins Hospital was one of these pioneers.  With better neuropathologic definition combined with more astute clinical observation the Foix-Alajouanine Syndrome (FAS) became part of a patient's differential diagnosis.

FAS usually occur in the thoracic spinal cord in "watershed" zone of the thoracic spinal cord.  Because this spinal area has the most tenuous arterial blood supply it is most prone to injury when its vascular nourishment becomes impaired.  The remittent leakage of blood from the A-V malformation promotes slowly progressive local arachnoid fibrosis (adhesive arachnoiditis) which physically and physiologically "chokes" the spinal cord.

Because the changes are slow the patient may not experience any neurologic symptoms until some event produces a situation akin to "the straw that broke the camel's back."  most individual afflicted with adhesive arachnoiditis have few in the way of clinical symptoms.

Focal Adhesive Arachnoiditis and Lumbar Puncture

We live in a medical era still characterized by lumbar puncture routinely utilized for the following purposes like Initiation of spinal anesthesia, Diagnostic taps to obtain spinal fluid samples, i.e. to rule out meningitis. It is not unusual for patients to experience, as a complication of spinal tap, continued leakage of cerebro-spinal fluid producing postural headache, lightheadedness and inability to function due to these complaints.  The commonly employed treatment for this is a "blood patch."  Blood drawn from a vein is purposely injected into the supposed epidural space as a means of "patching" the leaking fluid. Appropriate blood patches routinely introduce some blood into the subarachnoid space and inappropriate ones may introduce as much as 10-12cc of blood directly into the subarachnoid space. How much blood, introduced how often, is necessary to create adhesive arachnoiditis?  This question has not yet been answered.  We only know at this point in time, that blood, and its breakdown products, can serve to create adhesive arachnoiditis and  the introduction of any foreign body substance (for any purpose) into the subarachnoid space is not a wonderful idea.

The diagnosis of the syndrome of Foix and Alajounanine (FAS) can occur only when the clinicians involved in the case know that this entity exists and also understand adhesive arachnoiditis as a pathologic entity.  Even at the start of the new millennium few radiologists or clinicians possess this awareness.


When the spinal cord is damaged as a result of trauma, there is often bruising or bleeding from the cord itself, either as a result of tearing of surface vessels by stretch, or by physical damage from bone fragments.  This bleeding then can lead to scar formation between the spinal cord and the inner surface of the canal, known as the dura.  When this scarring occurs, the deformity can cause further loss of neurological function or pain, often in a delayed fashion, sometimes 10-20 years later.  When this occurs, the tethering can be cut so that the cord no longer is being tugged on with every movement of the body, and this can relieve or improve the symptoms.


Various surgical procedures, including cerebrospinal fluid (CSF) shunting or subarachnoid reconstruction, are available.
Shunting of CSF from the syringomyelia to the subarachnoid, pleural, or peritoneal space has been proposed to resolve the propagation of the syringomyelia or myelomalacia, but the effect of the procedure is not long lasting and revision surgery is needed rather frequently.
Microsurgical dissection of the arachnoid adhesion, with decompression of the subarachnoid space, is another approach and may achieve better and more long-lasting outcomes in selected cases.

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