vivax es una especie patógena que produce una tasa considerable de

The same principle applies during the motor examina- tion. In the presence of an upper motor neuron lesion (UMNL), typical patterns of weakness and facilita- tion are apparent in the limbs and trunk. A UMNL lesion will typically produce a ‘flexor pattern’ of facil- itation in the upper limbs with associated inhibition of the extensor muscle groups, with the opposite sce- nario being evident in the lower limbs. Thus, if the presence of a UMNL lesion has been identified through a detailed history and examination of tone, coordination and reflexes, prior to motor system test- ing the motor system examination would need to be expanded to evaluate all muscle groups in the limbs, neck and head (cranial nerve supply). In the absence of a CNS lesion the assessment of muscle strength can be limited to muscle groups suggested in the his- tory, i.e. the most likely myotome and myotomes above and below it (Harrison, 1996) with a screening examination of proximal muscle power (decreased in myopathies) and distal power (decreased in periph- eral neuropathy) (Table 5.4). Thus, a quick screen of power can be confined to shoulder abduction and fin- ger abduction in the upper limb, and hip flexion with the knee straight, and ankle dorsiflexion in the lower limb. The Medical Research Council (MRC) Scale (Medical Research Council, 1990) is the conventional grading scale for muscle power when assessing the PNS and can be seen in Table 5.5.

Coordination

Coordination is affected by proprioceptive loss (sen- sory ataxia) as well as cerebellar function (dysmetria, an inability to judge distance and control voluntary muscular action) and so clinical tests of coordination are not specific to cerebellar function; however, an assessment of the patient’s coordination can be

Table 5.2 Describing the main mechanisms of pain

Pain mechanism

Description

Peripheral nociceptive

Local sources within muscles, joints and soft tissues

Peripheral neurogenic

Sources in peripheral nerves, nerve roots and cranial nerves

Central Sources within neurons and synapses in the central nervous system

Efferent Pain related to efferent mechanisms, influenced by motor neurons including those of the autonomic nervous system Affective Related to neurons and circuitry more

Table 5.3 The expanded and contracted tone, coordination and reflex examination

Examination Test Rationale

Contracted Observe gait, facial movement and intricate function during subjective examination

Wrist circumduction Pronator catch Plantar response

Comparison of deep tendon reflexes with contralateral limb

Speed and control of intricate movements of speech, gait, writing and undressing revealed prior to formal testing

Upper limb tests of abnormal tone quick, sensitive and reliable (Donaghy, 1997)

Tests for spasticity

Observe for isolated deep tendon reflex loss in nerve root and peripheral nerve lesions and generalized loss in peripheral neuropathy (Fuller, 1993)

Expanded As above but expand with:

Lower limb tests of tone at hip, knee and ankle Finger/nose and or heel/shin tests

Reflex testing of all four limbs and jaw jerk (cranial nerve V); also abdominal reflexes and frontal lobe release signs (Fuller, 1993).

Similar testing procedure to upper limb tests with rapid rotations of the hip and flexion/extension of the knee and ankle observing for a spastic catch or rigidity (Perkin, 1992). Cogwheel rigidity is lead-pipe rigidity that may be associated with tremor (Donaghy, 1997). Both upper and lower limb tests of coordination performed

Observe for patterns of increased and decreased reflexes typical of patterns in UMNL

Table 5.4 The expanded or contracted motor examination

Examination Test Rationale

Contracted For general screening, a proximal muscle (myopathy) should be tested with a distal muscle (peripheral neuropathy) with the specific myotomes of the peripheral nerve or root thought to be implicated (Donaghy, 1997)

Muscle group testing restricted to comparison with the contralateral side, not necessary to test all the limbs and neck and head muscle groups

Test mid-range isometric muscle strength to ‘breaking point’ which represents the muscle’s maximum voluntary isometric contraction. Strong muscles like upper fibres of trapezius and quadriceps femoris should be placed in inner range to increase the mechanical advantage of the examiner. However, due to the length–tension relationship of the muscles, the starting positions for muscle testing should be standardized in order to improve the reliability of testing (Refshauge & Gass, 1995)

Expanded Test all four limbs to examine the distribution of weakness. Patterns of weakness are particularly important in the presence of UMNL signs. In the presence of UMNL signs examine the neck and face muscles (cranial nerves) (Fuller, 1993)

Use repeated testing to expand strength testing into examination for fatigue of muscle (Donaghy, 1997).

There are five patterns of muscular weakness: 1. UMNL – increased tone, increased reflexes,

pyramidal pattern of weakness (weak extensors in the UL and weak flexors in the LL)

2. LMNL – wasting, with or without fasciculation, decreased tone and absent or decreased reflexes 3. Muscle disease – wasting, decreased tone,

impaired or absent reflexes

4. Neuromuscular junction – fatigable weakness, normal or decreased tone and normal reflexes 5. ‘Functional weakness’ normal tone, normal reflexes

without wasting and with erratic performance of tests (Fuller, 1993).

quickly tested by the finger nose test and heel shin tests in the upper and lower limbs respectively (Harrison, 1996). These are conducted by asking the patient to reach out fully to touch the examiner’s finger and then return their finger to their nose. The heel shin test involves the patient placing one heel accurately on their opposite knee and then running it repeatedly up and down the anterior edge of the tibia. During both tests, observations for intention tremor, overshooting and ‘trick’ movements to stabi- lize the proximal limb are made. Again, if signs of incoordination are observed with these tests, the examination would be expanded to explore the dys- function further (see Table 5.3).

Reflexes

An upper motor neuron lesion (UMNL) results from a disruption of the pyramidal pathway at any point between the motor cortex and the anterior horn cell, whilst a lower motor neuron lesion (LMNL) results from a disruption of the pathway from the anterior horn cell in the motor nucleus and neuromuscular junction (Perkin, 1992). The most valid single test of UMNL is the assessment of the plantar response (Donaghy, 1997). This test, also known as the Babinski test (the unfavoured term), can be present immediately a lesion has occurred, well before sufficient spasticity has devel- oped to produce clonus or hypereflexia (Donaghy, 1997). The plantar response is a reflex response to a noxious stimulus on the lateral margin of the sole of the foot with the normal response, after the first

year of life, being plantarflexion of the toes with dorsiflexion of the ankle (Harrison, 1996). In the presence of a UMNL the hallux dorsiflexes and the toes fan. Due to the diagnostic value of this sim- ple test the details of conventional performance are detailed in Figure 5.2, with detail on interpretation and methods of varying the technique to account for ticklish and anxious patients. It must be remem- bered that, as with all examination procedures, a single test such as the plantar response, will never be perfectly accurate or adequate to form a clinical diagnosis in itself. The clinical diagnosis must be established from a synthesis of both history and physical features derived from the complete exami- nation, and consequently, the clinician should be cautious of over interpreting this sign.