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Myoclonus

Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a symptom and, generally, is not a diagnosis of a disease. The myoclonic twitches or jerks are usually caused by sudden muscle contractions; they also can result from brief lapses of contraction. Contractions are called positive myoclonus; relaxations are called negative myoclonus. The most common time for people to encounter them is while falling asleep ("sleep starts"), but myoclonic jerks are also a symptom of a number of neurological disorders. Hiccups are also a kind of myoclonic jerk specifically affecting the diaphragm. more...

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Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. They may occur infrequently or many times each minute. Most often, myoclonus is one of several symptoms in a wide variety of nervous system disorders such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, and Creutzfeldt-Jakob disease.

Anatomically, myoclonus may originate from lesions of the cortex, subcortex or spinal cord. The presence of myoclonus above the foramen magnum effectively excludes spinal myoclonus, but further localisation relies on further investigation with electromyography (EMG) and electroencephalography (EEG).

Familiar examples of normal myoclonus include hiccups and hypnic jerks that some people experience while drifting off to sleep. Severe cases of pathologic myoclonus can distort movement and severely limit a person's ability to eat, talk, and walk. Myoclonic jerks commonly occur in individuals with epilepsy. The most common types of myoclonus include action, cortical reflex, essential, palatal, progressive myoclonus epilepsy, reticular reflex, sleep, and stimulus-sensitive.

Types

Classifying the many different forms of myoclonus is difficult because the causes, effects, and responses to therapy vary widely. Listed below are the types most commonly described.

  • Action myoclonus is characterized by muscular jerking triggered or intensified by voluntary movement or even the intention to move. It may be made worse by attempts at precise, coordinated movements. Action myoclonus is the most disabling form of myoclonus and can affect the arms, legs, face, and even the voice. This type of myoclonus often is caused by brain damage that results from a lack of oxygen and blood flow to the brain when breathing or heartbeat is temporarily stopped.
  • Cortical reflex myoclonus is thought to be a type of epilepsy that originates in the cerebral cortex - the outer layer, or "gray matter," of the brain, responsible for much of the information processing that takes place in the brain. In this type of myoclonus, jerks usually involve only a few muscles in one part of the body, but jerks involving many muscles also may occur. Cortical reflex myoclonus can be intensified when patients attempt to move in a certain way or perceive a particular sensation.
  • Essential myoclonus occurs in the absence of epilepsy or other apparent abnormalities in the brain or nerves. It can occur randomly in people with no family history, but it also can appear among members of the same family, indicating that it sometimes may be an inherited disorder. Essential myoclonus tends to be stable without increasing in severity over time. Some scientists speculate that some forms of essential myoclonus may be a type of epilepsy with no known cause.
  • Palatal myoclonus is a regular, rhythmic contraction of one or both sides of the rear of the roof of the mouth, called the soft palate. These contractions may be accompanied by myoclonus in other muscles, including those in the face, tongue, throat, and diaphragm. The contractions are very rapid, occurring as often as 150 times a minute, and may persist during sleep. The condition usually appears in adults and can last indefinitely. People with palatal myoclonus usually regard it as a minor problem, although some occasionally complain of a "clicking" sound in the ear, a noise made as the muscles in the soft palate contract.
  • Progressive myoclonus epilepsy (PME) is a group of diseases characterized by myoclonus, epileptic seizures, and other serious symptoms such as trouble walking or speaking. These rare disorders often get worse over time and sometimes are fatal. Studies have identified at least three forms of PME. Lafora body disease is inherited as an autosomal recessive disorder, meaning that the disease occurs only when a child inherits two copies of a defective gene, one from each parent. Lafora body disease is characterized by myoclonus, epileptic seizures, and dementia (progressive loss of memory and other intellectual functions). A second group of PME diseases belonging to the class of cerebral storage diseases usually involves myoclonus, visual problems, dementia, and dystonia (sustained muscle contractions that cause twisting movements or abnormal postures). Another group of PME disorders in the class of system degenerations often is accompanied by action myoclonus, seizures, and problems with balance and walking. Many of these PME diseases begin in childhood or adolescence.
  • Reticular reflex myoclonus is thought to be a type of generalized epilepsy that originates in the brainstem, the part of the brain that connects to the spinal cord and controls vital functions such as breathing and heartbeat. Myoclonic jerks usually affect the whole body, with muscles on both sides of the body affected simultaneously. In some people, myoclonic jerks occur in only a part of the body, such as the legs, with all the muscles in that part being involved in each jerk. Reticular reflex myoclonus can be triggered by either a voluntary movement or an external stimulus.
  • Stimulus-sensitive myoclonus is triggered by a variety of external events, including noise, movement, and light. Surprise may increase the sensitivity of the patient.
  • Sleep myoclonus occurs during the initial phases of sleep, especially at the moment of dropping off to sleep. Some forms appear to be stimulus-sensitive. Some persons with sleep myoclonus are rarely troubled by, or need treatment for, the condition. However, myoclonus may be a symptom in more complex and disturbing sleep disorders, such as restless legs syndrome, and may require treatment by a doctor.

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Reducing the risk of cross-contamination from transmissible spongiform encephalopathies
From AORN Journal, 9/1/05 by Timothy A. Brendle

In response to recent reports from several major US medical centers regarding possible exposure of surgical patients to the virulent class of diseases known as transmissible spongiform encephalopathies (TSEs), (1,2) one institution developed guidelines to care for surgical patients with a preoperative diagnosis of "rule out TSE." The guidelines not only protect patients from accidental exposure to TSE, but they also protect nurses, surgeons, technologists, anesthesia care providers, housekeeping personnel, and sterile processing department staff members.

Transmissible spongiform encephalopathies is a catchall term for several prionic diseases, including bovine spongiform encephalopathy (ie, mad cow disease), Creutzfeldt-Jakob disease (CJD), variant CJD, and Gerstmenn-Straussler-Scheinker syndrome. Prions are proteins that attack the brain of humans and some animals and cause an array of neurological symptoms, including sleep pattern changes, fatigue, memory loss leading to presenile dementia, and, ultimately, death. (3,4) There are three theories related to how a TSE infection is contracted. Sporadic infections have no discernible cause or apparent origin. (5) Inherited infections (ie, in which there is a family history of the disease) account for about 10% to 15% of reported cases) Iatrogenic transmission (ie, exposure via a medical procedure or cross-contamination from contaminated surgical instruments) (5) is the focus of this article.

THE CASE FOR DISPOSABLE INSTRUMENTS

Recently reported incidents of surgical patients' possible exposure to TSE seem to share a common denominator--reused surgical instruments. (1,2) Prions have a high tolerance for current sterilization methods, including heat, chemicals, gas, and ionizing radiation. (6) Disinfectants and some tissue fixatives also have little effect on prions. (6)

Institutions that use "CJD-only" instruments and drills may present a threat to surgical patients as well. There is a risk that these instruments accidentally could be used on the wrong patient or be sterilized in the same autoclave cycle as other surgical instruments. Another risk is the possibility of using CJD-only instruments on a patient with a preoperative diagnosis of "rule out TSE," only to find that the pathology is benign. Now the patient may have been exposed inadvertently to TSE.

One solution to reduce the possibility of cross-contamination during surgical procedures on patients suspected of having TSE is to use disposable surgical instruments. (7,8) Some people will say that using disposable instruments is not cost effective or practical; depending on surgical need and the instrument company, a disposable CJD instrument tray could cost between $1,500 and $2,300. Others would argue, however, that reducing the real risk of iatrogenic transmission to a surgical patient should far outweigh this cost. Use of disposable instruments also reduces the number of personnel who could be exposed to infectious material.

ONE FACILITY'S TSE GUIDELINES

Staff members at one facility formulated a TSE/CJD policy in part following the guidelines set forth by the University of Iowa Hospitals and Clinics. (9) Criteria for performing a biopsy to rule out TSE usually are related to the presentation of specific symptoms or positive results of diagnostic tests. Symptoms that may indicate TSE include, but are not limited to,

* presenile dementia,

* myoclonus,

* electroencephalogram changes indicative of TSEs,

* cerebral spinal fluid protein elevation 14-3-3, and

* basal ganglia changes noted via magnetic resonance imaging scan. (4)

When a surgical patient presents with some or all of these symptoms, it is imperative that the surgeon inform the OR scheduler and infection control department personnel of the suspected diagnosis. Unless clinicians communicate with one another, no policy, standard of care, or state-of-the-art computerized scheduling system will be effective against future exposure of surgical patients to TSE.

This facility uses a computerized scheduling system that has a set of specific codes based on the posted procedure. If a surgeon schedules a patient for brain biopsy to rule out TSE, the code generated (ie, BRNBXCJD) is programmed to produce a warning message to the scheduler to initiate TSE protocols and precautions.

PREOPERATIVE. A procedure to rule out TSE is scheduled as the last procedure of the day or as the only procedure in a selected OR suite. The OR is stripped to a bare minimum of equipment and sup plies. Equipment should be limited to an anesthesia machine, OR bed, suction machine, electro-surgical trait, and back table. All trash cans are removed, with the exception of one biohazard receptacle and a sharps box. A large, disposable, impervious drape sheet is placed in the center of the room and taped in place, and the OR bed is centered on the sheet. The sheet helps contain any infectious material. The bipolar foot pedal cord is covered with a plastic bag, which extends at least 4 ft from the pedal and is taped in place. Each end of the OR bed is covered with impervious biohazard plastic bags and covered with a sheet (Figure 1). Anesthesia care providers are reminded to use only disposable supplies for intubation and ventilation.

[FIGURE 1 OMITTED]

INTRAOPERATIVE. All OR personnel wear disposable protective gowns, eye shields, masks, gloves, and shoe covers. This personal protective equipment is donned before the patient enters the room and worn for the entire procedure. Two circulating nurses are assigned to the procedure; one circulating nurse remains in the OR suite and the other acts as a "runner."

The scrub person opens a basic craniotomy supply pack along with the TSE disposable instrument tray (Figure 2). This tray is assembled with basic craniotomy instruments to help minimize cost to the patient. No other instruments are used, and no power equipment is allowed per the facility's policy. Typically, power equipment cannot withstand the stringent decontamination and sterilization cycles needed to provide a sterile, prion-free drill. A Hudson brace and Gigli saw are used to perform a basic craniotomy, and the cost of these items is minimal compared to the cost of a power drill. All of the facility's neurosurgeons were consulted when the TSE disposable instrument tray was created because surgical practice can vary from physician to physician (Table 1).

[FIGURE 2 OMITTED]

During the procedure, the scrub person and surgeon use a magnetic mat in the neutral zone and hands-free techniques to pass instruments and sharps. If an instrument is contaminated or dropped during the procedure, it is placed in the sharps box for incineration, and the second circulating nurse retrieves a peel-packed replacement instrument. The replacement instrument then is considered to be disposable.

When the brain biopsy is obtained by the surgeon, the scrub person places it in a closable container filled with formalin. The circulating nurse labels the container "presenile dementia/CJD-TSE precautions," and double bags it with a biohazard bag. The circulating nurse calls the attending pathologist and informs him or her of the possible contagion. The specimen then is hand-carried to the pathology department and hand-delivered to the pathologist.

POSTOPERATIVE. At the end of the procedure, all disposable surgical instruments are placed in a biohazard sharps box marked for incineration. All bed linens also should be placed in biohazard trash to be incinerated. All personnel must dispose of protective attire within the OR suite in biohazard trash. After the patient has left the surgical suite, housekeeping personnel are called in, and they perform their own TSE decontamination procedures.

A WORK IN PROGRESS

Policies and procedures for caring for a surgical patient with possible TSE are a work in progress. Until science has a better understanding of the etiology of this infectious protein, medical professionals must remain vigilant in asepsis and patient advocacy. Currently, performing an invasive brain biopsy is the only definitive way to diagnosis this condition, but recent research suggests that a simple urine test possibly could provide the diagnosis. (10) For now, facilities may want to consider using disposable surgical instruments for brain biopsy to rule out TSE as the standard to reduce the risk of cross-contamination and, thus, improve the standard of care for all surgical patients.

The author acknowledges Sally Peters, RN, neurosurgical staff nurse; Phyllis O'Neal, RN, neurosurgical staff nurse; and Pamela Fogle, RN, infection control practitioner coordinator, Medical University of South Carolina, Charleston, SC, for their input and support during the preparation of this article.

Editor's notes: This article depicts one facility's guidelines that meet or exceed current recommendations. Publication of this article does not imply AORN endorsement. For more information, see "Recommended practices for high-level disinfection," and "Recommended practices for cleaning and caring for surgical instruments and powered equipment," in Standards, Recommended Practices, and Guidelines (Denver: AORN, Inc, 2005).

NOTES

(1.) D Wahlberg, "Emory Methods Questioned. 516 Patients Told Risk of Exposure to Mad Cow-Like Disease 'Remote,'" The Atlanta Journal-Constitution, 2 Oct 2004, A1.

(2.) T Corwin, "MCG Scare Halts VA Surgeries," The Augusta Chronicle, 13 Jan 2005.

(3.) V M Steelman, "Creutzfeldt-Jacob disease: Decontamination issues," Infection Control and Sterilization Technology 3 (September 1996) 32-39.

(4.) "Infectious prion diseases," McGraw-Hill's AccessMedicine, http://www.access medicine.com (accessed 2 February 2005).

(5.) "About CJD," Creutzfeldt-Jacob Disease Foundation, Inc, http://www.cjdfoundation .org/cjdisease.html (accessed 13 July 2005).

(6.) World Health Organization Communicable Disease Surveillance and Control, "WHO infection control guidelines for transmissible spongiform encephalopathies. Report of a WHO consultation, Geneva, Switzerland, 23-26 March 1999," World Health Organization, http://www.who .int/csr/resources/publications/bse/whocdscsraph 2003.pdf (accessed 13 July 2005).

(7.) "Recommended practices for high-level disinfection," in Standards, Recommended Practices, and Guidelines (Denver: AORN, Inc, 2005) 314.

(8.) "Recommended practices for cleaning and caring for surgical instruments and powered equipment," in Standards, Recommended Practices, and Guidelines (Denver, AORN, Inc, 2005) 397.

(9.) V M Steelman, "Prion diseases--An evidence-based protocol for infection control," AORN Journal 69 (May 1999) 946-967.

(10.) N L Belkin, "Creutzfeldt-Jacob disease--Identifying prions and carriers," AORN Journal 78 (August 2003) 204-210.

Timothy A. Brendle, RN, CNOR, is a perioperative clinical nurse leader, neurosurgery, Medical University of South Carolina, Charleston, SC.

COPYRIGHT 2005 Association of Operating Room Nurses, Inc.
COPYRIGHT 2005 Gale Group

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