<unk>  is an inflammatory condition of the arachnoid mater or 'arachnoid', one of the membranes known as meninges that surround and protect the nerves of the central nervous system, including the brain and spinal cord. The arachnoid can become inflamed because of adverse reactions to chemicals, infection from bacteria or viruses, as the result of direct injury to the spine, chronic compression of spinal nerves, complications from spinal surgery or other invasive spinal procedures, or the accidental intrathecal injection of steroids intended for the epidural space. Inflammation can sometimes lead to the formation of scar tissue and adhesion that can make the spinal nerves "stick" together, a condition where such tissue develops in and between the leptomeninges. The condition is extremely painful, especially when progressing to adhesive<unk> . Another form of the condition is<unk>  ossificans, in which the arachnoid becomes ossified, or turns to bone, and is thought to be a late-stage complication of the adhesive form of<unk> .
Arachnoiditis
Idiopathic intracranial hypertension
Subdural empyema
Brain abscess
Cavernous sinus thrombosis
Subdural hematoma
Labyrinthitis
Pseudosubarachnoid hemorrhage