Introduction:
The posterior fossa is a type of cranial fossa or cavity on the floor of the skull. It is a small cavity that includes the brainstem and the cerebellum. Particular situations, like traumatic injury to the brain, bleeding, brain tumor, or hereditary developmental situations known as Chiari malformation, condense the cerebellum and brainstem, pushing parts of those structures into the spinal canal.
Chiari malformation is a typical and dominant symptomatic hereditary craniocervical malformation. Radiological examination confirms diagnosis when the cerebellar tonsils are discovered five millimeters or in the lower grade of the foramen magnum seen on magnetic resonance imaging. Surgical therapy is meant if there is symptomatic herniation in the tonsils or syringomyelia. The primary surgical treatment for Chiari malformation without craniocervical instability is posterior fossa decompression. It is done with or without duraplasty.
What Is Posterior Fossa Decompression?
Posterior fossa decompression is a surgical method that extracts bone from the skull, back area, and spine to broaden the site for the tonsils and brainstem. A minimally invasive procedure indicates the quantity of bone removal required to resuscitate standard cerebrospinal fluid flow effectively, and it relies on Chiari's anatomy and dimensions.
The amount of bone disposal is the same in every procedure, that is, in the endoscopic method or standard open approach. It is also significant to comprehend that specific minimally invasive techniques are utilized in kids whose skull is developing, which cannot be suitable for grown-ups. Spinal fusion is achieved along with posterior fossa decompression procedure in specific conditions with spine fluctuation, which is not stable, can be because of scoliosis, Ehler-Danlos syndrome, or any bone anomaly. Rods and screws are placed to strengthen the skull and neck vertebrae structurally.
What Are the Indications of Posterior Fossa Decompression?
Posterior fossa decompression is accomplished to lessen the cerebellum and spinal cord tension. The pressure in the posterior fossa can induce headaches, drowsiness, loss of balance, and optical disorder, and in some rare cases, it also affects speech and causes liability and numbness. In Chiari malformation, there is an obstruction to the discharge and the path of cerebrospinal fluid; in a few cases, they are asymptomatic. However, in patients, it can induce specific debilitating symptoms, like headaches, numbness, liability, and the evolution and formation of spinal cord cysts called syringomyelia.
What Are the Preoperative Measures Taken In Posterior Fossa Decompression?
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Preoperative selection is made in patients based on an abnormal accumulation of cerebrospinal fluid in the spinal cord, known as a syrinx. A Chiari malformation is a case that causes obstruction in the cerebrospinal fluid flow. This condition can be confirmed by an MRI scan and is inducing severe symptoms. The patient should be well-educated about the procedure. A neurosurgeon will explain the procedure, its imperilment, and its advantages. Every doubt of the patient should be cleared in this period.
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A thorough medical history should be taken during this preoperative period, which includes any medical conditions like allergies, medications, vitamins, hemorrhage that occurred in the past, anesthesia responses, and any surgeries done previously.
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An excellent detailed history was taken about the current medications taken by the patient.
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Certain tests should be done preoperatively, including specific blood tests, and an electrocardiogram should be accomplished a few days before the surgery.
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A checkup and discussion should be done with the primary care physician regarding the stoppage of medications the patient is taking and confirm the patient is fit for the procedure.
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The patient is informed to discontinue the administration of all non-steroidal anti-inflammatory medicines, including Ibuprofen, Naproxen, and blood thinners like Warfarin, Aspirin, and Clopidogrel, at least seven days before the procedure.
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The patient is asked to quit nicotine and alcohol intake at least one week prior and two weeks post-surgically. This is done to prevent bleeding and recovery difficulties.
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The patient is informed to clean the skin and hair with dial soap before the procedure. It destroys bacteria and decreases surgical site infections.
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The patient is asked to fast from midnight before the procedure. After that, drugs can be administered with minimal drinks of water.
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The patient is asked to avoid doing any dental treatment for at least three weeks or any type of other surgery for this procedure.
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Patients are asked to inform the surgeon if they develop any manifestations of infection, like a rising in temperature, cold, or flu, before the procedure.
What Happens During Posterior Fossa Decompression?
A posterior fossa decompression process is done under general anesthesia and typically lasts two to three hours. The method implies an average of five to six-centimeter length incisions made at the center of the head's posterior location and the neck's upper portion. In that location, a small unit of bone, an average of more than two centimeters in diameter on the floor of the skull, is cleared. This method is called a suboccipital craniectomy.
Usually, a unit of the C1 vertebra present beneath is also extracted. This procedure is also called a cervical laminectomy. Next, the dura, the outermost membrane present close to encircling the brain, is flared, and an additional tissue graft is attached; this is known as expansile dura plasty done to enable more additional area in the posterior fossa. Once the surgery is done, the incision is sealed with stitches or staples.
Conclusion:
The outcome of decompression surgery relies on the extension of the Chiari malformation and the involvement of any prior brain and nerve damage that occurred before the procedure. On average, eighty-five percent of patients have significant alleviation of symptoms. Nevertheless, patients may resume having residual manifestations from syringomyelia.
If damage in the spinal cord has evolved to be permanent, surgery could not provide relief from the harm that occurred. Exertional headache and pain in the neck region react better to decompressive surgery as most of the brainstem indicates consumption difficulties, facial pain, numbness, and hoarseness of the voice. Repetition of constriction or obstacle to the cerebrospinal fluid occurs rarely.
