BRAIN INJURY, 1999, VOL. 13, NO . 3, 213 ±

216

A case of amnestic syndrome caused by a
subcortical haematoma in the right occipital lobe
O SAMU M ASUO,
SH IN ICH IR O M A ESH IM A ,
KEN JI KUBO, TOM OAK I TERADA,
K U N IO N AK A I, T O RU IT AK U RA an d
N O R IH IK O K O M A I
Department of Neurological Surgery, Wakayama Medical College, Wakayama, Japan
(Received 21 August 1998; accepted 13 October 1998 )
A case of an amnestic syndrome caused by a subcortical haematoma in the right occipital lobe is
reported. A 62-year-old right-handed man presented with a sudden onset of headache to the hospital.
On admission, he had a left homonymous hemianopsia, disorientation and recent memory disturbance, but had normal remote memory and digit span. Computed tomography (CT) and magnetic
resonance imaging (MRI) revealed a subcortical haematoma in the right occipital lobe. These findings
suggest that the patient’s amnesia was caused by a lesion of the retrosplenial region in the nondominant hemisphere.

Introd uctio n
In 1987, Valenstein described a patient with amnesia associated with an arteriovenous malformation located between the splenium of the corpus callosum and the
trigone of the left lateral ventricle [1]. He called this syndrome retrosplenial amnesia
and suggested that this memory deficit was due to an interruption of an alternative
pathway from the hippocampus to the anterior thalamus. Following that initial
description, additional cases have been reported [2± 4]. However, in the prior
reports, retrosplenial amnesia was caused by a retrosplenial lesion in the dominant
hemisphere. Here, the first case of retrosplenial amnesia caused by a non-dominant
hemisphere lesion is reported.

Ca s e rep ort
A 62-year-o ld right-handed man was admitted as an emergency to hospital because
of the sudden onset of headache on the morning of 6 March, 1994. On admission,
the patient was alert. Neurologic exam ination revealed a left homonymous hemianopsia. He had neither motor paresis nor sensory disturbance. A CT scan performed on admission demonstrated a subcortical haematoma in the right occipital
Correspondence to: Dr Osamu Masuo, Department of Neurological Surgery, Wakayama Medical
College, 7± 27 Wakayama 640, Japan.
Brain Injury ISSN 0269± 9052 print/ISSN 1362± 301X online Ñ 1999 Taylor & Francis Ltd
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O. Masuo et al.

lobe with ventricular penetration (figure 1a). An angiogram did not reveal any
abnormal blood vessels. Therefore, on the 4th hospital day, a stereotactic evacuation
of the haematoma was performed. A post-operative CT scan demonstrated total
removal of the haematoma (figure 1b). MRI 6 months following the haemorrhage
revealed the cyst cavity in the right medial occipital lobe (figure 1c). A sagittal MRI
section showed destruction of the right lateral corpous callosum.

Neuropsychologic examinations
On the 10th postoperative day, neuropsychologic testing was performed (table 1).
The mini-mental status exam ination scale was 16/30. Digit span was performed
successfully for up to seven digits, and word fluency (animal names) was 10 per
minute. Aphasia, ideomotor, or ideational apraxia were not observed. Tactile naming in the left hand was normal. Neglect of the left side was seen in line bisection,
line cancellation, and figure copying tests.
On the Wechsler Adult Intelligence Scale-Revised (W AIS-R), the patient’s
verbal IQ was 92 and his performance IQ was 70. His full IQ was 75. These results
demonstrated a mild impairm ent of intelligence, especially in performance.
His memory function was impaired. On the Wechsler memory scale, all tasks
were impaired, and his memory quotient was 75. On the Benton visual recognition
test and auditory verbal learning test, both verbal and non-verbal tasks were disturbed.

Table 1. Neuropsychological examination
Mini-mental state ( /30)
Word fluency ( /min)
Raven’ s CPM ( /36)
WAIS-R
Verbal IQ
Performance IQ
Full scale
Wechsler memory scale (MQ)
Information
Orientation
Mental control
Logical memory
Digit span
Visual reproduction
Associative learning
Benton Visual Retention Test
Immediate recall
Delayed recall
Auditory Verbal Learning Test
Immediate recall
Delayed recall
Recognition
Miyake’s Associate Learning Test
Meaningful ( /10)
Meaningless ( /10)

13
7
13

22
8
29

26
8
29

92
70
75
67
3/6
0/5
6/9
2/24
8/15
5/14
3/21

94
78
90
76
4/6
4/5
6/9
2/24
9/15
5/14
3.5/21

94
81
88
88
3/6
4/5
7/9
3.5/24
10/15
6/14
8/21

4/10
2/10

4/10
2/10

3/10
3/10

5, 6, 5, 3, 4/15
1/15
10/15

2, 0, 5, 5, 6/15
0/15
9/15

4, 6, 4, 6, 5/15
5/15
10/15

2± 4± 5
0± 0± 0

5± 7± 7
0± 0± 0

5± 8± 8
1± 2± 1

Amnestic syndrome and subcortical haematoma

215

(a)

(b)

(c)
Figure 1. (a) A CT scan on admission demonstrated a subcortical haematoma in the right occipital lobe with
ventricular penetration. (b) A post-operative CT scan demonstrated total removal of the haematoma. (c) MRI
after 6 months revealed the cystic cavity in the right medial occipital lobe.

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O. Masuo et al.
Clinical course

Serial neuropsychologic tests were performed for 6 months. The patient’s minimental status score and IQ gradually improved. Neglect of the left side also resolved
within a few weeks. However, all evaluations of memory function did not show
remarkable improvement.
D is c us s io n
Valenstein [1] hypothesized that retrosplenial amnesia was caused by a lesion in the
pathway between the hippocampus and anterior thalamus. Patients with retrosplenial amnesia present with anterograde amnesia more frequently than retrograde. In
fact, all previously reported cases demonstrated anterograde amnesia, and three cases
also had retrograde amnesia [2± 4]. Recent reports suggest that the retrosplenial
region plays an important role in processing information involved in memory
and learning [3]. Unlike the previously reported cases, this patient had a nondominant retrosplenial lesion. Generally the destruction of the non-dominant retrosplenial region leads to topographic disorientation without amnesia. In this case, a
topographic disturbance was not clearly present. This case represents the first report
of a non-dominant retrosplenial amnesia. The authors hypothesize that a right
retrosplenial lesion causes amnesia by a disruption between the hippocampus and
anterior thalamus.
A lesion of the pathway from the hippocampus to the anterior thalamus in the
dominant hemisphere impairs verbal memory. The interruption of this pathway in
the right hemisphere also leads to a disturbance of visual memory. Likewise, Milner
et al. [4] suggested, from a retrospective analysis of temporal lobectomy cases, that a
left temporal lobectomy could cause a disturbance of verbal memory, but a right
temporal lobectomy disrupts visual memory. However, the present case of a nondominant lesion demonstrated a disturbance of both the verbal and visual memory.
This observation suggests the existence of a close interaction between the right and
left hemispheres in memory function.
Referenc es
1. V ALENSTEIN, E., B OW ER, D., V ERFAELLIE, M. et al.: Retrosplenial amnesia. Brain, 11: 1631± 1646,
1987.
2. V AN, G. T. and W YSS, J. M.: Connection of the retrosplenial granular cortex in the rat. Journal of
Comparative Neurology, 315: 200, 1992.
3. M ORI , E., Y A MA DORI , A. and M ITANI , Y. : Left thalamic infarction and disturbance of verbal
memory. Annals of Neurology, 20: 671± 676, 1986.
4. M ILNER, B., COKIN, S. and TEUBER, H.: Further analysis of the hippocampal amnestic amnesia
syndrome. A 14-year follow up study of HM. Neuropsychologia, 6: 215± 234, 1968.