Ординатура / Офтальмология / Английские материалы / Clinical Neuro-ophthalmology A Practical Guide_Schiefer, Wilhelm , Hart_2007
.pdf
Chapter 4 U. Schiefer, J. Schiller, W. Hart
Visual field defects |
Pathogenesis/differential diagnosis |
4.9.2.4Refraction scotomas with characteristic fundus changes
λOcular wall ectasia (usually inferonasal)
λProminent tilting of the optic disc
Additional testing, when indicated:
λ Fundoscopy
λ Streak retinoscopy
λ Repeat perimetry with updated refraction
No respect for the vertical meridian, and expansion of the isopters with use of an appropriate lens
4.9.2.5 Homonymous Hemianopsias
Homonymous hemianopsia to the left with good congruence; no macular sparing causes severe loss of reading ability
λRetrochiasmal lesion in the contralateral hemisphere (e.g., a tract lesion [on the right side], or widespread damage to the retrogeniculate visual system [on the right]
λVascular disease (in about 75 % of patients)
λInfarction (hemorrhagic or occlusive)
λArteriovenous malformation or aneurysm
λSpace-occupying lesions (in about 15 % of patients)
λPrimary brain tumor
λMeningioma
λMetastases
λInflammation, e.g., multiple sclerosis
λTrauma (up to 2% of patients)
A retrogeniculate lesion of the contralateral hemisphere
Homonymous hemianopsia to the left with good congruence and distinct sparing of the macular field, allowing retention of fluent reading ability
Additional testing indicated for homonymous hemianopsias:
λHistory
λSwinging flashlight test
λFundoscopy (asymmetric, bilateral optic atrophy caused by tract lesions, see ■ Fig. 8.23)
λMRI, CT, MR-angiography
λArteriography only when necessary
λNeurological consultation
λInternal medicine consultation
50
Perimetry
Visual field defects |
Pathogenesis/differential diagnosis |
Indicates a retrochiasmal lesion [on the right]
This pattern occurs with isolated lesions of the optic tract
– such lesions are uncommon, being found in about 4% of cases
An incomplete homonymous hemianopsia on the left
with poor congruence, no macular sparing and consequently poor reading ability
This pattern is associated with lesions of the [left] lateral geniculate body and is quite rare (see ■ Fig. 3.6)
Wedge-shaped, homonymous defect on the right, straddling the horizontal meridian, with some congruence, no macular sparing and consequently poor reading ability
This pattern suggests disease in the [left] temporal lobe – the inferior portions of the optic radiations in the [left] cerebral hemisphere are damaged (see ■ Fig. 3.7c)
Homonymous sectors of loss in the right superior quadrant with some congruence, macular sparing and consequent retention of good reading ability
see also Animation 3.3
51
Chapter 4 U. Schiefer, J. Schiller, W. Hart
Visual field defects
Sector-shaped, homonymous defects in the right inferior quadrant with good congruence, no macular sparing and poor reading ability
Small homonymous sectors of loss in the right superior quadrant with very good congruence; in addition it respects both the vertical and horizontal meridians, no macular sparing, poor reading ability
Pathogenesis/differential diagnosis
Suggests a parietal lobe lesion [on the left side]; (the superior portions of the [left] optic radiations are damaged – see ■ Fig. 3.7c)
Indicates damage to the visual cortex [on the left side] (caudal portion of the optic radiations damaged –
see ■ Fig. 3.7c); respects the border between the superior and inferior quadrants, which are divided by the calcarine fissure; the lesion has damaged the inferior half of the primary visual cortex
see also Animation 3.3
52
Perimetry
Visual field defects |
Pathogenesis/differential diagnosis |
4.9.2.6 Bilateral homonymous hemianopsias
Bilateral homonymous quadrants of loss (so-called checkerboard pattern) with good congruence, no macular sparing and poor reading ability
Bilateral homonymous quadrant defects – altitudinal field loss
“Pseudoconcentric” constriction with apparent congruence, macular sparing, and good reading ability; localized respect of the vertical meridian (see areas hatched in red) allows use of the differential diagnosis of a “truly” concentric constriction, as in 4.1.1
Usually bilateral occipital lobe infarcts
(In this example the lower half of the visual pathway is damaged on the right side, and the upper half is damaged on the left side)
Bihemispheric, retrochiasmal lesions (in this example they are both located in the lower half of the retrochiasmal pathway)
Widespread damage to both upper and lower halves of the posterior pathways due to bihemispheric retrochiasmal disease
53
Chapter 5
Diagnosis of Pupillary Disorders
H. Wilhelm and B. Wilhelm
Pupillary testing serves two purposes, first, to find disorders of pupillary function itself, and second, to detect disorders of the afferent visual system and the autonomic innervation of the eye. A systematic approach will help significantly with interpretation of the findings. The examination should be done in a logical order, since the pupillary system responds in a logically predictable way. Tests that yield no useful information can only create confusion.
Anatomic and Physiologic Fundamentals
of the Pupillary System
There is a great deal of useful information in the anatomy and physiologic responses of the pupillary system, information that the clinician can put to immediate good use. Three aspects of pupillary behavior are of particular relevance during a clinical examination:
1.The size and speed of pupillary constriction in response to a light stimulus of medium strength are proportional to the logarithm of the luminance intensity of the stimulating light. This being the case, pupillary responses can be used as a test of the eye’s sensitivity to light. This is the basis for the interocular comparisons made during the swinging flashlight test as described in Chap. 2.
2.Normal pupillary reactions are highly variable and are influenced by many variables (status of accommodation, emotions, vigilance, drug effects). This variance is both interand intraindividual, which diminishes the value of individual observations and requires multiple repetitions of a test, before a pathological finding can be confirmed.
3.The pupillomotor centers in the pretectal midbrain – a region of nuclear centers anteroventral to the quadrigeminal plate – receives neural signals evoked by retinal illumination and transmitted by way of the optic tract (■ Fig. 5.1). Pupillomotor afferents are not separated by eyes, but rather by visual hemifields. Each side of the pretectum in turn sends signals via multisynaptic connections to both sides of the Edinger-Westphal nuclei. Neurons with their somas in these nuclei send their
Fig. 5.1. Schematic overview of the anatomy of the pupillary light reflex arc. By way of the optic tract the afferent path (1) of the pupillary system projects to the dorsal midbrain (pretectum, 2). From there, the signal is carried to the Edinger-Westphal subnucleus in the nuclear complex of the oculomotor (third) cranial nerve. The oculomotor nerve innervates the ciliary ganglion (3), from which the short posterior ciliary nerves arise and enter the eye to innervate the pupillary sphincter (4). Not to be overlooked are afferents in this reflex system that arise in the visual cortex and project to the pretectal region, providing another input pathway that participates in the reflex process
55
Chapter 5 H. Wilhelm, B. Wilhelm
56
57
Flow diagram. Diagnostic procedures for pupillary disorders. LR Light reaction, RAPD relative afferent pupillary defect
Disorders Pupillary of Diagnosis
Video 5.1
Chapter 5 H. Wilhelm, B. Wilhelm
axons by way of the third cranial nerve to the ipsilateral ciliary ganglion from where postganglionic parasympathetic fibers innervate the eye via the short posterior ciliary nerves, terminating at the pupillary sphincter. This anatomically bilateral sharing of neural input has the important consequence that damage to the afferent visual pathways that lead to the Edinger-Westphal nucleus cannot cause an anisocoria. Thus, anisocoria is never a sign of an afferent disturbance, but is always a sign of an efferent pupillary disorder. This is the physiologic foundation for the tests to be described in the following sections of this chapter.
What Is Needed For Pupillary Testing?
Pupillary testing requires two bright lights (e.g., an indirect ophthalmoscope and a bright flashlight), a pocket gauge for measuring pupillary diameters, neutral density filters, a slit lamp, a topical solution of 5% cocaine, occasionally a 1% solution of hydroxyamphetamine (where available), pilocarpine 0.1% and 1.0%, and phenylephrine 2.5% eye drops.
• Pearl
For presbyopic examiners, a generous near correction is needed for adequate study of pupillary sizes, shapes, and movements. Pupillary examinations are usually best done in a dimly illuminated, nearly dark room (see below), which makes proper correction of the examiner’s refractive errors particularly important.
Systematic Examination of the Pupils
First step: Confirm that the pupils respond to light. Only in the dark can the pupils really show how well they can react, so be sure that the room light is as dim as convenience will allow. The patient should be asked to look into the distance, to limit intrusion by the miosis of the near reflex. Using a strong light source (such as an indirect ophthalmoscope) stimulate both eyes simultaneously. If both pupils visibly and symmetrically constrict, go to the second step.
If one or both pupils do not appear to react, a pathological state in need further examination has been found (go to the fourth step).
Second step: Compare the pupillary diameters to one another. Examination and interocular comparison of the pupillary diameters determines whether the autonomic (efferent) innervation of the eye is intact. If there is an anisocoria, repeat testing of both pupils’ responses to a strong, binocular light stimulus.
• Pearl
These two steps can be combined. Illuminate both eyes from a position below the visual axis and then slowly bring the light source closer to the eyes. Determine whether the pupils are symmetrical in size and whether both constrict equally.
Third step: Do the swinging flashlight test. This step compares the afferent pupillary responses of one eye to the other. (The swinging flashlight test is described in detail in Chap. 2).
When a pupil is poorly reactive or does not react to a light stimulus, the swinging flashlight test cannot be done in the usual way since the test requires that both pupils react equally to light. Moreover, if there is an anisocoria, the requirements for this test are somewhat different. Experience has found that when there is an interocular difference of 0.5 mm or more in pupillary diameter, the test is best done by judging the movements of the pupil that has the better light reaction, comparing its direct and consensual responses. This method is more completely described in Chap. 2.
Anisocorias of 0.3 mm or less are not usually visible. If normal responses have been found up to this point, the test is concluded. It should be recorded as, “Pupils sizes and light responses are equal; there is no relative afferent pupillary defect.”
Fourth step: Examination of pathological findings. After completion of the first three steps, the following pathological states are possible:
1.A relative afferent pupillary defect (RAPD)
2.An anisocoria with normal responses to light in both eyes
3.A monocular or bilateral deficit in light responses
Further Testing When Pupillary Signs Are Abnormal
Relative Afferent Pupillary Defect
When an RAPD is found, the cause must be identified. This process is described in some detail in Chap. 2. If the cause cannot be found, perimetric examination of both eyes is necessary.
Anisocoria with Bilaterally Normal Pupillary Reactions to Light
Dilation Test
The dilation test uses a comparison of the speed of pupillary dilation of both eyes after extinguishing a bright light stimulus. It determines whether there is evidence of a problem with sympathetic innervation of the pupil(s). A prob-
58
Diagnosis of Pupillary Disorders
Fig. 5.2. Typical responses of the pupils in the normal state and in the classical pupillary disorders during routine examination. a Testing of anisocoria and the pupillary light response. b Responses to the swinging flashlight test with normal afferent function. c Responses found in monocular disorders of the afferent portion of the reflex arc. 1 Inspection in the dark; 2 inspection with lights on: no anisocoria, and with either normal responses or signs of an
afferent defect; 3, 4 light reactions for the interocular comparisons during the swinging flashlight test with normal responses and no relative afferent pupillary defect (RAPD); 5, 6 left RAPD; 7–12: pupillary light responses in the case of a widely dilated pupil in the right eye that does not respond to light; 9, 10 no RAPD; 11, 12 in the presence of an RAPD on the right
59
Video 5.3 Video 5.2
Chapter 5 H. Wilhelm, B. Wilhelm
lem is that the test is done in a darkened room. Ideally, one should use an infrared video system to examine pupillary movements in the dark, i.e., after turning the light stimulus off. A practical alternative is to use a separate, weak light source to illuminate both eyes at a tangential angle from below, so that both pupils are visible and a minimum area of retina is being illuminated in each eye. It is best not to look at the eye with the brighter stimulus, since this causes light adaptation of the examiner’s eyes, making it difficult to see the dimly illuminated pupil.
When the pupils dilate well and with no speed difference between them, the anisocoria is likely to be physiologic. Physiologic anisocoria of greater than 1 mm is very uncommon, so when the difference is greater than 1 mm, use of the cocaine test is necessary (see below). Also, when the smaller pupil dilates more poorly, the cocaine test is likewise indicated.
!Note
Observation of the pupils in the dark with infrared light is simpler and more effective than are examinations done under dimly illuminated conditions. Infrared video recording is now easy to implement. Video camcorders commonly have a “night” or “zero lux” setting, which is a form of infrared video recording. The barrier filter of the camera can be removed, and an infrared light source turned on. Such devices are reasonably inexpensive, making their use for pupillary testing very attractive.
Cocaine and Hydroxyamphetamine Tests
The cocaine test is indicated in three situations:
1.For anisocoria greater than 1 mm and normal pupillary light reactions
2.For slower dilation of the smaller pupil
3.For ptosis ipsilateral to the smaller pupil (suspected Horner’s syndrome)
Cocaine retards the reuptake and inactivation of noradrenalin within the synaptic cleft. Thus, it is an indirect sympathomimetic. When sympathetic innervation is intact, there is a constant rate of release of noradrenalin into the synapse, and cocaine blocks its reuptake, causing an accumulation of the neurotransmitter, and resulting in pupillary dilation. If the anisocoria is physiologic, the smaller pupil dilates more than does the larger pupil, reducing the anisocoria.
Drops of 5% cocaine are instilled in both eyes (all pharmacologic pupil testing should be done symmetrically, comparing one eye to the other). This preparation is usually available at hospital pharmacies. If there is any uncertainty about the completeness of an application to either
eye, the drop should be immediately repeated. When testing infants and small children, use of a 2.5% solution of cocaine is recommended. The diameters of both pupils are measured before and 1 h after instillation of the drops, using the same levels of illumination for both measures. It is usually sufficient to measure the pupils’ diameters with a pocket card that has semicircles of various diameters arrayed along one margin. If greater precision is desired, the measurements should be done with photography.
• Pearl
If 1 h after cocaine instillation there remains a difference between the pupillary sizes of 1 mm or more, this should be accepted as reasonable proof of Horner’s syndrome (■ Fig. 5.3). If the anisocoria is less than
0.3 mm, it is most likely physiologic. However, one should take into account that 5% cocaine produces an average dilation of 2.1 mm in normal pupils and 0.5 mm in pupils affected by Horner’s syndrome. Only 3% of Horner’s-affected pupils respond with a dilation of more than 1 mm, so when cocaine produces a dilation of 1.5 mm or more, Horner’s syndrome can be effectively ruled out.
Thus, cocaine testing clearly differentiates physiologic anisocoria from Horner’s syndrome. ■ Table 5.1 lists the limiting values. In cases of doubtful results, the test should be repeated. In the United States, where random testing by employers is common, subjects tested with cocaine should be given certificates indicating that they have been exposed to cocaine as a medical testing agent. The effect of topical administration of a 5% solution of cocaine to the eye can be detected in urine samples for several days.
Fig. 5.3. Horner’s syndrome (right side) before and after cocaine test
60