Secondary Schizophrenia (14 page)

tem, which is then involved in recognition of stimulus by a cortical pattern recognition system
[174].

During normal listening to patterned sound such as
The literature relating to gustatory hallucinations
music, auditory input is processed by two mechanisms,
occurring in organic disorders consists mainly of case
which operate in a hierarchical manner. The pattern
reports in which the nature of the experiences varies
is first perceived, and then encoded into memory or
considerably. In contrast, the olfactory experiences of
recognized. It is possible that reduced auditory input
patients with a range of “organic” pathologies are much
because of deafness allows spontaneous activity within
more uniform in their quality. As described by patients

the system. This may take the form of positive feed-with epilepsy, the perceived smells are unpleasant and
Introduction – Section 1

usually of burning, rotting, fecal, or other organic
patients of color. The black African description of the
material. Patients who describe olfactory or gustatory
hallucinations was often related to death or decay. Nde-hallucinations are likely to describe or exhibit other
tei and Singh
[188]
identified olfactory hallucinations
symptoms depending on the underlying condition.

in 25% (13/51) of Kenyan patients with schizophrenia
Isolated hallucinations in either modality are very rare
but in none of the 29 patients with other psychiatric
in either psychiatric or organic states.

diagnoses. In a second Kenyan study, only 3% of 141

patients with schizophrenia were found to have olfac-

tory hallucinations
[189].
None of these studies exam-

ined for the presence of gustatory hallucinations. The
World Health Organization ten-country study of 1,288

patients with first-episode schizophrenia, published in
Schizophrenia

1992, identified OHs in 13% of patients in developed
Olfactory and gustatory hallucinations occur in a
countries and 9% of those patients from developing
significant minority of patients with schizophrenia.

countries
[190].

For example, Pearlson and colleagues
[185]
stud-In summary, OHs have been described in patients
ied 131 patients with schizophrenia and identified
with differing diagnoses including schizophrenia,
olfactory/gustatory hallucinations in 17%/12% of the
affective disorders, and eating disorders. Gustatory
patients. In schizophrenia, olfactory, gustatory, and
hallucinations have been found in patients with
tactile hallucinations are usually “fellow travellers”

schizophrenia but few studies have investigated for
with auditory hallucinations. In one study, 2% of
their presence in other psychiatric conditions. The hal-patients with olfactory/gustatory hallucinations, 84%

lucinations tend to be of an unpleasant nature though
of patients with tactile hallucinations, and 84% of
good descriptive accounts of the quality of the smells
patients with VHs also described auditory hallu-is lacking in the psychiatric literature.

cinations
[6].
The presence of tactile and olfactory/gustatory hallucinations was highly correlated to

each other and both types, but not with auditory or

visual hallucinations, nor with the severity of delusions.

Epilepsy

Other psychiatric disorders

An epileptic aura is “that portion of the seizure which
occurs before consciousness is lost and for which
The diagnostic specificity of olfactory hallucinations
memory is retained afterwards”
[191].
Early studies
in patients with psychiatric illness was addressed
found that 750 of 1,039 epilepsy patients described
in a study of 131 patients with schizophrenia, 21

226 different types of epileptic aura
[192]
whereas a
patients with depression, 31 patients with eating dis-more recent study identified an aura in 64% of 290

orders, and 77 normal control subjects
[186].
Olfac-patients
[193].
The commonest auras described by
tory hallucinations (OHs) were described by patients
patients across these studies were of epigastric sen-from the three patient groups but not in the control
sations, motor phenomena, affective states, déjà vu,
group (schizophrenia 35%, depression 19%, and eat-and vertiginous sensations. In patients unselected for
ing disorders 29%) and the prevalence was not signif-the type of epilepsy, about 1% describe OHs
[192,

icantly different by group. Patients with schizophrenia
194],
whereas in studies of patients with temporal lobe
and depression generally described unpleasant smells
epilepsy the figures range from 0.03% to 13%
[156,

whereas the eating disorder patients described halluci-

193, 195,
196, 197, 198,
199].
Gustatory hallucinations
nations that were food related and generally pleasant.

are also relatively uncommon with prevalence rates of
ranging from 0.2%
[192],
to 2%
[193],
to 11%
[195].

Cultural variables

Daly
[196]
coined the term “uncinate fits” in a
Olfactory hallucinations have also been noted in
description of 55 patients of whom 20 (36%) had
non-Western cultures. Teggin and colleagues
[187]

olfactory and gustatory phenomena associated with
reported olfactory hallucinations in 59% of black
seizures of various etiology. Daly postulated that the

African patients compared to 20% of white and 27% of
uncus, which he considered to the cortical center for
Chapter 3 – Secondary hallucinations

smell was the common anatomical structure for these
nomic, or visual symptoms. Based on their observa-seizures. Patients with olfactory hallucinations usu-tions and their review of the literature, the authors
ally described neutral, unrecognisable odors, although
speculate that amygdala pathology is critical in the
both pleasant and unpleasant odors were experienced.

generation of olfactory auras.

In the patients with olfactory auras, associated auras
Acharya and colleagues identified 14 patients with
and sensations were common but not quantified by the
OHs in a group of 1,423 patients (0.9%)
[198].
Seven
author. Sixteen patients described gustatory halluci-patients described the smell as unpleasant (burning,
nations with their descriptions, including unpleasant,
sulphur), five were neutral, and two said the smell
sour/bitter, salty, metallic, or neutral.

was pleasant (e.g., flowers). Five of the patients had
Lennox and Cobb conducted a survey of U.S. neu-associated gustatory auras, one had abdominal aura,
rologists and physicians and showed that 56.2% of the
one visual, four had psychic auras, and one heard the
1,527 cases described 327 different sensations which
sound of the ocean. Only 2 of 14 (14%) of patients had
met the author’s criteria for an aura
[192]
. There were
isolated olfactory hallucinations and 12 of 14 (86%)
no differences in the experience of an aura identified
of patients described associated auras. Eight of nine
by gender or epilepsy etiology. Auras were found to be
patients who went on to surgery were free of seizures
more frequently associated with intellectual disability
and aura following surgery. Like Chen and colleagues
(“mental deterioration”) and duration of epilepsy. Fif-

[197]
the authors propose that the amygdala is the site
teen patients (1.0%) had OHs that were described as
of the olfactory auras and that the presence of an olfac-disagreeable (9), peculiar (2), like bananas, camphor,
tory aura provides potential anatomical localization to
or the smell of ironing (1 each), whereas only 2 patients
the amygdala.

described gustatory phenomena. It is not possible from
the data available or the text of the article to ascertain
the relationship of the olfactory auras to any clinical
Other neurological disorders

variables.

Olfactory hallucinations have been more commonly
Fried and colleagues investigated the relationship
described than olfactory associations in the context of
between auras and focal epilepsy pathology before
other neurological disorders. Olfactory hallucinations
and after epilepsy surgery
[156].
The 90 patients in
have been reported to precede the motor manifesta-the study (43 patients with hippocampal sclerosis,
tions of Parkinson’s disease
[199]
and to have benefited
30 patients with other temporal lobe lesions, and 17

from l-dopa treatment. A longitudinal study of Parkin-patients with extratemporal lesions) described 125

sonian patients treated with l-dopa found that the
auras. Of the 11 patients (12.2%) who experienced
early development of hallucinations (predominantly
olfactory/gustatory auras (the study grouped these two
visual but also tactile, auditory, and olfactory) sig-together), nine had hippocampal sclerosis. The qual-naled either a comorbid psychotic illness or an evolv-ity of the auras was not described in the study. Fol-ing parkinsonism-plus syndrome
[200].
In contrast, a
lowing surgical resection, only 1 of these 11 patients
study of 98 patients with Parkinson’s disease did not
experienced ongoing olfactory/gustatory auras. This
identify any patients with OHs and only one patient
patient had a pathological diagnosis of hippocampal
with gustatory hallucinations
[201].

sclerosis.

Olfactory hallucinations have been reported as the
Chen and colleagues also assessed 217 patients who
presenting symptom for cluster headaches
[202]
and
had undergone temporal lobectomy for intractable
migraines
[203].
The smells reported by migraine suf-temporal lobe epilepsy before and after surgery
[197].

ferers tended to be unpleasant and include descrip-Twelve (5.5%) of the patients described olfactory
tions such as decaying animals, burning cookies,
auras, but only one patient had a gustatory aura.

cigars, peanut butter, and cigarette smoke. Olfac-At postsurgical follow-up, no patients had ongoing
tory hallucinations have been reported as an unex-auras. All patients described the olfactory experience
pected complication of the administration of intra-as unpleasant with descriptions of the smell as “fetid,
venous
[204]
and oral
[205]
caffeine boluses in normal
rotten, or stinking” food, burning, charred things,
and panic disorder subjects during research studies of
alcohol, or medicine. One patient had isolated olfac-panic and anxiety disorders.

tory hallucinations, whereas the other 11 patients most
Olfactory

hallucinations

of

gasoline,

feces,

commonly described abdominal sensations, fear, auto-urine, and garbage have been described in patients
Introduction – Section 1

with chronic cocaine use
[206],
whereas a smaller
Delusional parasitosis

proportion of this group described an inability to
The role of tactile hallucinations in the delusional par-detect strong tastes in food, which the authors termed
asitosis is contested. In this disorder, the patient expe-

“negative gustatory hallucinations.” In all subjects,
riences a monohypochondriacal conviction that he or
the hallucinations occurred in association with
she is infested with insects
[213, 214].
Some authors
hallucinations in other modalities.

believe that tactile hallucinations are the primary disorder in this condition
[215, 216]
whereas others
[217,

218]
view the delusion to be primary. In one of the
largest samples of subjects reported
[219],
the present-

ing complaint in the majority of 52 subjects was insects

crawling over the head or body, although this report
does not allow the determination of whether sensa-The only strong data set revealing the likely rate of
tions preceded the delusional explanation, if the delu-tactile (also known as “somatic” or “haptic”) halluci-sions triggered the sensation, or if both commenced
nations in the population comes from the Epidemi-simultaneously.