What is Postdural Puncture Headache?
Postdural puncture headache is often severe and localized over back of the head. The Postdural puncture headache is also known as occipital headache. The character of postdural puncture headache is throbbing and continuous. Headache does not respond to pain medications. Postdural puncture headache is caused by continuous leakage of cerebrospinal fluid from laceration, crack or hole in dural membrane. The three membranes cover brain and Spinal cord. Cerebrospinal fluid lies between 2nd and 3rd layer of membrane, also known as mater. The 3 membranes are known as pia, arachnoid and dura mater. The CSF is also found in ventricles within the brain tissue in addition to subarachnoid space, which surrounds brain and spinal cord. The three membranes which surround brain also continues around spinal cord. The space which contains cerebrospinal fluid lies between pia and arachnoid mater and known as subarachnoid space. There is no space between pia mater and spinal cord, pia mater is closely attached to spinal cord. Similarly, there is no space between arachnoid and dura mater, since both the membrane are closely adhered to each other.
What is Dural Puncture?
Dural puncture occurs when physician attempts to perform procedure or surgery close to epidural space, subarachnoid space or spinal cord. The dural laceration or punctures are caused by sharp surgical instruments or tip of the needle. The structural damage of surface of dura also includes arachnoid membrane, since both the membrane are adhered to each other. Thus any laceration or penetration of dura also causes crack or hole in arachnoid membrane that results in exposure of subarachnoid space. So, puncture of dura exposes the subarachnoid space to epidural space. Even tiny exposure of subarachnoid space caused by tip of thinnest spinal needle results in cerebrospinal fluid leak in to epidural space. The slow or rapid loss of cerebrospinal fluid from subarachnoid space follows severe headache. Such headache caused by dural puncture is known as Postdural puncture headache. The loss of cerebrospinal fluid decreases pressure within subarachnoid space, which is expressed with symptoms like severe pounding headache. Dural puncture can be minor or major.
Causes of Minor Dural Puncture-
- Spinal Anesthesia- Spinal anesthesia is performed by placing needle in subarachnoid space. The local anesthesia is injected through the needle in to subarachnoid space. In few cases multiple attempts are made to place needle in epidural space. The dural puncture causes tiny hole in dura and subarachnoid mater, which closes immediately after removal of needle because of retraction of elastic fibers of membrane. In few cases less than 0.1% the hole does not close and CSF leak continues. The continuous leak of CSF results in symptoms of headache.
- Epidural Anesthesia- The procedure is performed either to inject local anesthetics or place the epidural catheter in the epidural space. In most cases the procedure is never causes any problems. In less than 0.25% cases the needle may touch dural surface and make a tiny puncture with tip of needle resulting in CSF leak.
Causes of Major Dural Puncture-
- Trauma- Major dural laceration is observed after industrial accident or auto injury. The accelerated impact caused by sharp objects in the area of middle of the back causes penetrating injury. Deep penetration of sharp object into dura causes severe laceration of dura and arachnoid membrane. Such injury is extensive and causes substantial laceration of dura.
- Surgery- Surgical procedure to treat disc, facet joint or spinal cord tumor often causes laceration of dura.1 Such laceration is almost all cases repaired during surgical procedure. In few cases small laceration is undiagnosed during surgery and cerebrospinal leak continues after surgery. The post-surgery CSF leak along the sutured incision of dura is also observed in few cases following surgical procedure. In such cases CSF leaks through the gap between the sutures.
What Causes Postdural Puncture Headache?
The subarachnoid space around spinal cord is also connected to brain. Loss of cerebrospinal fluid following continuous leak through puncture or lacerated dural cracks and decreases the pressure within the subarachnoid space surrounding spinal cord and brain. Thus the drop of pressure within subarachnoid space is observed in spinal cord as well as brain. Sudden drop of pressure within subarachnoid space covering brain which is enclosed in skull also affects the outline of vessels like arteries, veins and lymphatics. These vessels around the brain swells up within skull to fill the loss of space created by loss of brain CSF. The increased size of pulsating vessels within brain causes pounding and throbbing headache.
How is Postdural Puncture Headache Diagnosed?
History of Headache- The history of severe headache, which begins 2 to 3 hours after back surgery, spinal anesthesia or epidural procedure suggests possible cause of headache could be dural puncture or laceration. Similarly, history of severe headache following work or auto accident resulting in blunt or penetrating back injury suggest possible dural injury. The history of headache also suggests intensity of post spinal headache become severe in sitting or standing position. Headache subsides or intensity decreases when patient lies down supine.
Diagnostic Lumbar Puncture- The diagnostic lumbar puncture procedure involves placing the needle in subarachnoid space and then checking the CSF pressure. The pressure in subarachnoid space is checked following placing the tiny 22 to 25-gauge spinal needle in lumbar subarachnoid space. The opposite end of the needle is connected to manometer to check the pressure. Simultaneously biochemical test is performed to check CSF protein and lymphocyte count. The loss of CSF causes increased concentration of CSF protein and lymphocytes count.
Magnetic Resonance Imaging (MRI)- MRI study of brain and spinal cord is performed. The tiny needle puncture over dura is often not observed in MRI films and images. MRI of the brain suggests diffuse dural enhancement and sagging of the dural coverings around brain. The films also indicate obliteration of basilar cisterns and enlargement of pituitary gland.2
How is Postdural Puncture Headache Treated?
Treatment of Minor Postdural Puncture Headache-
Blood Patch- Minor Postdural Puncture Headache are treated with blood patch treatment. The blood patch is performed by anesthesiologist. The epidural needle is placed in epidural space at the level where the spinal leakage is suspected. Same time assistant draws blood up to 15 ccs from same individual. The 10 to 15 cc of blood is slowly injected in epidural space. Procedure is performed under X-Ray guideline. Following injection of blood, puncture space gets covered by blood. The lodged blood within the cracks clots resulting in stoppage of CSF leak.
Continuous Flow of Epidural Saline- The recent published article suggests alternative to blood patch is to place a catheter in epidural space and inject 6 cc of normal saline per hour.3 The volume injected matches the volume loss resulting in balancing the pressure. The treatment for postdural puncture headache may last for 2 to 3 days and gives time to heal the wound.
Treatment of Postdural Puncture Headache Caused By Major Laceration
Surgical Repair- Postdural Puncture Headache caused due to major laceration cannot be treated with blood patch. The continuous leak causes severe loss of cerebrospinal fluid resulting in continuous headache. The treatment option for postdural puncture headache due to major laceration is surgical repair of dural tear.
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Continuous epidural pumping of saline contributes to prevent and treat postPostdural puncture headache.
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