Secondary Schizophrenia (148 page)

[66],
who denied any localization of hallucinations
4. Patients with simple hallucinations may not

to anatomy or any association with the blind field.

report them because they are short lasting,

An important aspect of the anatomy underlying the

regarded as insignificant, or are not even noticed.

occurrence of VH is the set of connections between the
different areas. This hodological feature is discussed at
Within selected groups (mostly of people with

length by ffytche
[96].

visual disease), the estimates vary from 10% to 51%

[67,
100, 101, 102, 103,
104].
Visual impairment (even
total blindness) does not necessarily lead to VHs
[100].

Also, with a progressive disease such as AMD, halluci-

What determines the total duration of

nations may commence long after the initial diagnosis
hallucinations and why do they usually

of the disease
[105].

eventually cease?

Course and outcome

Associated with the degree of complexity of the hallu-CBS hallucinations are usually not unpleasant and
cinations is the total period over which they are man-in virtually all cases eventually disappear. They do
ifest. In general, it is the case that complex hallucina-not normally require treatment although, of course,
tions persist for a long time, sometimes years, whereas
the underlying cause of the hallucinations must be

simple hallucinations last days or weeks. To take again
determined and treated. Patients are generally relieved
the extreme cases of Bonnet’s grandfather and myself,
when they are told that they have no mental illness.

his hallucinations lasted for several months, whereas
CBS has been treated successfully with antiepileptic
mine lasted for 10 to 12 days. Another example of

medication, for example, carbamazepine
[106],
and
a mild deafferentation associated with a short-lasting
with serotonin reuptake inhibitors
[107].
The success-manifestation of VHs is the linkage of these two fea-ful treatment of VH using a steroid in a patient with
tures during macular translocation
[17].

temporal arteritis without effect on the loss of vision
According to the deafferentation theory, a de-

emphasizes the importance of cerebral ischemia in

afferented neuron becomes hyperexcitable and may

the development of VH
[108].
The same conclusion is
develop an increased spontaneous activity. It follows
reached when VH occurs after strokes
[109].
In one
that re-afferentation (reinnervation) should reverse
case CBS resulting from a stroke was completely sup-

this sequence. The nervous system has this universal
pressed by transcranial magnetic stimulation of the

property that denervation or disuse causes sprouting
occipital cortex, an effect not understood but obviously
of nearby neurons
[98].
In the visual system, there
of therapeutic importance
[110].

are several examples of this, for example, a retinal
lesion causes sprouting of cortical neurons in the vicin-ity of the deafferented synapses
[98, 99].
It would be
Implications for clinical practice

expected that sprouting would occur at all deafferented
Correct diagnosis is most important. The first step is
synapses. However, sprouting is a fairly localized pro-to establish that there is no psychiatric condition. The
cess and, if the lesion is extensive, there may be few or
second step is to get some evidence about the likely
no nearby intact afferent neurons. On the other hand,
cause of the hallucinations (visual impairment, drugs,
a small injury would create few deafferented synapses
other diseases). The patient should then be referred to
374

and a speedy recovery could be expected.

the appropriate specialist. Walterfang and colleagues
Chapter 30 – The Charles Bonnet Syndrome

provide a very useful discussion of psychiatric consul-Patients should be encouraged to make careful
tation
[111].

notes and sketches of their hallucinations, especially
if they are of the simple (geometric) type. For

Suggestions for future research

example, an attempt should be made to determine the

size of the hallucination and of its component parts.

Whenever the opportunity presents itself, an imaging
This can be done by superimposing the hallucination

technique should be used at the time of a hallucina-

against a feature in the room, for example, a picture on
tion in order to localize the relevant anatomy. There is
the wall. Three measurements are needed: the dimen-

some evidence that Single Photon Emission Computed

sions of the feature (picture), the fraction occupied by
Tomography (SPECT) may be the most sensitive tech-

the hallucination, and the distance of the patient from
nology
[112].

the feature. From these data, the size of the VH and its
There is evidence that VHs may be an early sign of

component parts (in degrees) can be determined from

dementia
[2,
113, 114, 115].
The occurrence of VHs
trigonometric tables. Size should always be reported
without peripheral visual pathology may indicate a

in degrees because the size in centimeters will vary
central defect not restricted to the visual system. It is
with the distance at which the eyes are focused. The
advisable to keep track of all such cases. In particular,
position of the VH in relation to the point of gaze

if dementia does develop, it should be asked whether
(above, below, left, right) should be noted. These data
the antecedent hallucinations give any predictive clue,
may help to relate the hallucination to an anatomical
for example, were they simple or complex?

feature.

375

Related Concepts – Section 4

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