nerve damage as a result of epidural - temporary neurologic deficits

Temporary neurologic deficits

Temporary neurologic deficits are loss of sensation and/or motor function following labor epidural. The incidence reported in published studies varies greatly from study to study. It is also not clear if these symptoms are cause by epidural itself or the process of childbirth.

If after the epidural the patient develops loss of sensation or motor function it is called neurologic deficit. If it does not resolve after a year this deficit is considered to be permanent. Paralysis following epidural hematoma is the example of permanent neurologic deficit. If symptoms resolve and the patient’s neurologic function fully recovers this deficit is temporary. In some publications temporary deficits are often referred to as transient. Though correct from the terminology point of view, the use of the word “transient” sometimes leads to mixing up temporary loss of neurologic function with the Transient Neurologic Syndrome (TNS), which is a complication of neuraxial anesthesia that is characterized by a specific set of symptoms and is discussed in the separate chapter.

Some neurologic disturbances after neuraxial block do not fit into known categories of complication and are difficult to explain. Clinical medicine deals with the human body,  something that is much more complicated than the most sophisticated piece of machinery  ever designed by engineering minds. Sometimes the body behaves in strange and unexplained ways. Case report that follows illustrates this.

31 year old Mrs. M requested epidural for childbirth. Her pregnancy was uncomplicated and she had no previous history of any medical condition. In other words she is a patient typical for labor ward. By the time the anesthetist arrived the patient was in considerable pain, and it was decided to perform combined spinal-epidural block. The procedure went smoothly, and labor pain was controlled within minutes. Several hours later the woman delivered a healthy boy and the epidural catheter was removed. By this time it was late evening, and the patient fell asleep.

After waking up the next morning Mrs. M discovered that she cannot move her hips and as the result is not able to walk. Usually, after stopping the epidural the sensation and movement are affected for some time, until local anesthetic wears off. The recovery seldom takes longer than a few hours, and the symptoms presented by our patient drew immediate attention. The anesthetist on call that day examined the patient and found severe weakness in the hip flexors on both sides. There was no impairment of sensation anywhere in the legs. Paranoid like all anesthetists about the possibility of spinal hematoma he requested urgent MRI which did not show any pathology in the spinal cord and surrounding tissues. The patient was re-assured that there is nothing wrong and it is the matter of time – a day or two – for the symptoms to go away.

It is the fact that labor itself may cause neurologic problems. The nerves that originate from lumbar plexus and supply the upper leg pass through the pelvis. During labor the head of the fetus may exert considerable pressure on the area where these nerves are located. Usually it is not a problem. However, if the head is large the pressure on the soft tissues in the pelvis will be higher than usual, and if labor is prolonged, the head pressing on the nerves harder and longer than usual may result in nerve injury, on one or both sides. Typical symptoms of such injury are weakness of the quadriceps muscles and impaired sensation in the thigh, usually more so on one side.

Returning to Mrs. M, the next day her situation did not change, and she was still unable to lift the legs and could not walk without the help of the walking frame. She also started becoming anxious. She was referred for further examination to the neurologist who, on the basis of clinical examination, diagnosed her with a rare neurological condition, Guillian-Barre syndrome. For the purpose of current discussion it is sufficient to mention that in light of this clinical situation and presenting symptoms this diagnosis was highly unlikely.

The patient spent next several days in the hospital with no further worsening of her symptoms or improvement. Then, without warning or apparent cause, the symptoms quickly improved, and shortly thereafter the woman walked out of the hospital without help and went home. During the phone call from her obstetrician few days later she confirmed that her legs are functioning normally, just like before her childbirth.

Final diagnosis in this case is unknown. Cases of strange and unexplained loss of sensation and/or motor function after labor epidurals are sometimes presented in clinical literature. In all cases the symptoms disappear within days and neurological function returns to normal without any consequences. It is possible that in some patients neural tissue reacts differently to local anesthetics and takes considerably longer to recover from their action.

Statistical data regarding temporary neurological deficits after epidurals or spinals is unclear and unreliable. The review of serious neurological complications mentioned in the chapter on paralysis following neuraxial block and referenced below attempted to clarify this topic. This review analyzed data published between 1966 and 2005 and selected 27 adequately designed studies that reported epidural haematoma, epidural abscess and neurological deficits following epidural or spinal blocks in obstetric patients. The combined number of patients in the selected studies was 1.37 million.

The problem common for reviews of this kind is that there are no accepted standards on the reporting of complications and their causes. In many reports the results of treatment and outcomes, as well as other important details, are often omitted. Overall this meta-analysis identified 254 cases of transient neurologic injury out of 987,000 patients in fifteen studies. Transient neurological deficit was defined as impairment of function lasting less than a year. In almost all cases only symptoms were described, without any link between the injury and labor epidural. Therefore it was impossible to distinguish between neurologic deficits caused by the epidurals and those resulting from labor itself or other causes. The estimated rate of transient neurologic injury was 1 in 3,900 women, or 257 per million. In studies published after 1990 the incidence was lower, 1 in 5,537, or 180 per million.

To make the situation more complicated, six studies with 290,000 women reported 34 neurologic injuries of unspecified duration. Because it is possible that these injuries were transient, the authors of the review analyzed them together with the known transient injuries. The inclusion of these patients in the statistical analysis brought the incidence of transient neurological deficit down to 1 in 4,300 women, or 230 per million, or, in studies published after 1990, 1 in 6,700 women, or 150 per million.

Another problem with presented data was that in individual studies the rates of transient injuries varied from as low as 1 per million to as high as 1000 per million. In general, larger studies reported considerably lower rates of transient neurologic injuries than smaller ones, and even lower incidence in studies published after 1990. While it makes sense to place more significance in larger studies the fact remains that the real incidence of this complication is unknown.

The problem of drawing conclusions in regards to transient neurological deficits also lies in the fact that the details of the event are often not reported. The term “neurologic injury” covers the whole spectrum of symptoms, from an area of numbness of the skin to complete paralysis. Obviously, one is more significant to the patient than the other, but the absence of detailed reports makes distinguishing between the two impossible.

There is a tendency to associate labor epidural with complications, even though often there is no evidence of direct link between them. For instance, despite the abundant evidence to the contrary, epidural are still commonly blamed for low back pain after pregnancy. Whenever a problem involving nervous system develops in a patient who just had epidural anesthesia it is only logical to suspect that epidural might be the cause. In such situations anesthetists do just that, suspect the worst and make sure that the patient is thoroughly investigated and serious epidural complications are excluded. However even when this is done and epidural is excluded as the cause of adverse effects, the fact that epidural did take place remains in the memories of those involved in the care of the patient and creates false sense of association. The case presented in this chapter is still referred to by the obstetrician involved as “Mrs. M who couldn’t walk after epidural”.

In summary, unexplained neurological symptoms are sometimes observed after labor epidurals. At this stage it is not clear if such symptoms are related to the actual epidural block or the process of pregnancy and childbirth. More research is necessary in this area in order to make definite conclusion.

References: 

Ruppen W, Derry S, McQuay H, Moore A. Incidence of Epidural Hematoma, Infection, and Neurologic Injury in Obstetric Patients with Epidural Analgesia/Anesthesia.
Anesthesiology 2006; 105:394–9

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Dr. Eugene Smetannikov is a practicing anesthesiologist with the interest in obstetric anesthesia. He is the author of the most comprehensive book on the subject, The Truth About Labor Epidural