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Lumbar Punctures

Lumbar punctures provide invaluable information if the local culture allows them to be done and if the laboratory can analyze the specimen. In children <5 years old, consider using a short small-gauge hypodermic needle; a butterfly needle works well in infants. For children >5 years old, use a standard lumbar puncture needle, if one is available. Otherwise, a longer small-gauge hypodermic needle may work, depending on the child's size.

Lumbar puncture needles may need to be reused. While this is potentially dangerous, it may be safer to reuse these needles than to reuse hypodermic needles. The obturator allows large material to be cleaned out of the needle's core. After cleaning, the needles should be steam autoclaved. If that is not possible, high-level disinfection by boiling has been recommended.1 To do this:

  1. Put the needles into a pan and cover them with 3 cm of potable water. Put the lid on the pan and bring the water to a boil. Once it begins to boil, keep it boiling for 15 minutes.

  2. While holding the lid on the pan, pour out the water without letting the needles fall out. This is not as easy as it sounds; practice this before you boil the needles.

  3. Leave the nearly dry needles in the covered pan until they are needed. Never put them anywhere else.

Psychogenic Disorders and Malingering

Patients with psychogenic neurological disorders may present with bizarre motor findings and neurological tests that indicate a functional disorder (described below). They usually will have normal muscle tone, no atrophy or fasciculations, and no ataxia, although they may try to simulate it. The following are a number of quick, easy tests that suggest a patient may be malingering—or not. In resource-poor settings, you will have to rely on these simple tests; in other settings, they can save clinicians time and effort.

The Hoover Crossed-Leg Test is for leg strength. A supine person who tries to lift his straight leg against gravity or resistance will push down (for leverage) with the other heel. To do the test, the examiner asks the patient to lift the affected leg while keeping one hand under the patient's other heel. No or little pressure on the examiner's hand while the person says he is trying to lift his leg signifies malingering—as long as both legs are not affected. A more effective modification is for the examiner to put a thumb over both ankles while doing the test (Fig. 26-1). This provides additional resistance to lifting the leg and also provides information on the relative strength exerted by each leg.

The Crossed-Hand Test (Fig. 26-2) is used to discover whether a complaint of unilateral hand numbness is valid. Have ...

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