Perineural Cyst

A disorder that is characterized by the presence of cerebrospinal fluid-filled nerve root cysts most commonly found at the sacral level of the spine, although they can be found in any section of the spine, which can cause progressively painful radiculopathy.

Epidemiology

The annual incidence of perineural cysts is estimated at approximately 5%, although large cysts that cause symptoms are relatively rare with annual incidence estimated at less than 1/2,000. Women are affected more frequently than men.

Clinical description

Patients with perineural cysts present with pain in the area of the nerves affected by the cyst, muscle weakness, difficulty sitting for prolonged periods, loss of sensation, loss of reflexes, pain when sneezing or coughing, swelling over the sacral area, parasthesias, headaches, sciatica, and bowel, bladder and sexual dysfunction. The cysts typically occur along the posterior nerve roots and can be valved or nonvalved. The main feature that distinguishes perineural cysts from other spinal lesions is the presence of spinal nerve root fibres within the cyst wall or in the cyst cavity.

Etiology

There are a number of conditions that can cause the cysts to become symptomatic, including traumatic injury, heavy lifting, childbirth, epidurals, and trauma to the spinal cord. It has also been observed that the herpes simplex virus can cause the body chemistry to change and that perineural cyst symptoms worsen during herpes virus outbreaks.

Diagnostic methods

Diagnosis is based on magnetic resonance imaging (MRI), computed topography (CT) or myelogram of patients experiencing lower back pain or sciatica.

Differential diagnosis

The main differential diagnoses are meningeal diverticula and long arachnoid prolongations, which can be distinguished by rapid filling on myelography compared to the delayed filling of perineural cysts. Differential diagnoses also include herniated lumbar discs, arachnoiditis and, in females, gynecological conditions.

Genetic counseling

The majority of perineural cysts are sporadic. However, in some cases cysts have been observed among relatives, suggesting the possibility of a familiar trait with autosomal transmission.

Management and treatment

Treatment involves lumbar drainage of the cerebrospinal fluid, CT scanning-guided cyst aspiration, decompressive laminectomy, cyst and/or nerve root excision and microsurgical cyst fenestration and imbrications. However, surgical treatment for perineural cysts is complicated by postoperative pseudomeningocele and intracranial hypotension, and recurrence of the cyst. Pain therapy may offer a nonsurgical alternative for the treatment of symptomatic perineural cysts.

Prognosis

Those who have progressive and prolonged symptoms may experience neurological damage if the cysts continue to compress nerve structures.