Key-words:
Immunosuppressed host - nocardiosis - ruptured mycotic cerebral aneurysm
Introduction
Nocardia is a gram-positive rod belonging to the actinomycete Nocardia family, Nocardia
order.[[1]] They are widely present in clod, and recently, the prevalence of the opportunistic
infection nocardiosis, which affects compromised hosts, has increased.[[2]],[[3]]
Here, we present the case of a 22-year-old woman, who was immunosuppressed, with a
ruptured intracranial aneurysm caused by a Nocardia infection and required surgery.
Pathological analysis of the aneurysm clearly indicated the presence of Nocardia.
Cases of ruptured cerebral mycotic aneurysm caused by Nocardia infection and showing
the pathology of intraaneurysm Nocardia are rarely reported.[[4]]
Case Report
The patient was a 22-year-old woman diagnosed with adult-onset Still's disease and
received chronic steroid and immunosuppression therapy for 5 years. She presented
with a sudden disturbance in consciousness. The head computed tomography scan revealed
subarachnoid hemorrhage (SAH) (World Federation of Neurosurgical Societies: Grade
III) and intracerebral hemorrhage [[Figure 1]].
Figure 1: Head computed tomography scan at the onset of subarachnoid hemorrhage demonstrates
diffuse subarachnoid hemorrhage with intracranial hematoma
Digital subtraction angiography (DSA) showed a small aneurysm at the bifurcation of
the right middle cerebral artery (M2-3) [[Figure 2]]. Preoperative cardiac ultrasonography revealed vegetation on the posterior wall
of the heart, measuring approximately 7 mm × 8 mm × 10 mm; therefore, mycotic ruptured
aneurysm with infective endocarditis (IE) was suspected. Emergent trapping of the
ruptured aneurysm of M2-3 middle cerebral artery, hematoma removal, and decompression
craniotomy was performed. In the pus-filled aneurysm, the wall of the aneurysm was
turbid and white and had irregularities [[Figure 3]]a. Pathological analysis showed the destruction of the aneurysm wall structure [[Figure 3]]b, and Gram-positive filamentous bacteria were observed in the necrosis surrounding
the aneurysm [[Figure 3]]c and [[Figure 3]]d.
Figure 2: Digital subtraction angiography at the onset of subarachnoid hemorrhage demonstrates
a small aneurysm at the right M2-3 bifurcation (red arrow). (a) Anteroposterior view,
(b) Lateral view, (c) 3D Rotational Angiography
Figure 3: Clinical and pathological findings of aneurysm (a) The aneurysm filled with pus,
which leaked out from the point of destruction of the aneurysm wall (*). The aneurysm
wall appears white and turbid with irregularities (b) Pathological analysis demonstrates
an internal elastic lamina (arrow head), intravascular lumen (*), expanded media (**),
destruction of internal elastic lamina (arrow), and persisting outer membrane (double
arrows) (c and d) Gram-positive filamentous bacteria detected in the necrosis surrounding
the aneurysm
Blood culture was performed after the surgery because mycosis was observed in the
aneurysm sample. Gram-positive rods were also noted in the blood culture another 4
days later, and nocardiosis was identified 11 days after performing the blood culture.
We determined that the cause of her cerebral mycotic aneurysm ruptured was nocardiosis.
Combination therapy with imipenem/cilastatin (IPM/CS) and amikacin was started and
was continued for 3 months. As a hyposensitization therapy, trimethoprim/sulfamethoxazole
(TMP/SMX) administration was initiated at 40 days postoperatively and was continued
for 6 months. Her symptoms of disturbed consciousness, cognitive function, and hemiparesis
gradually improved. She was transferred to another hospital 7 months after medical
treatment and rehabilitation.
Discussion
Nocardia is a Gram-positive rod bacterium belonging to the actinomycete Nocardia family,
Nocardia order, which is widely present in clod.[[1]] The risk of infection has recently increased, especially in patients on steroid
and immunosuppressant therapy for a long time and those with high blood sugar levels,
lymphoma, malignant tumor, and human immunodeficiency virus infection.[[2]],[[3]]
Our present case is a 22-year-old woman diagnosed with adult-onset Still's disease
and received chronic steroid and immunosuppression therapy for 5 years.
There were not any clinical signs of endocarditis or multi-organ failure, but cardiac
ultrasonography immediately after the onset of SAH showed vegetation of the posterior
wall of the heart, so mycotic ruptured aneurysm with IE was suspected.
Nocardiosis is classified into three groups: pulmonary form, skin form, and dissemination
form. Hematogenous dissemination could cause IE and lead to the development of a mycotic
cerebral aneurysm.[[5]],[[6]],[[7]] Mycotic aneurysm associated with IE occurs in approximately 2% of all patients
with cerebral aneurysms[[8]] and appears more commonly in the middle cerebral artery distal branch.[[9]]
In our case, DSA demonstrates a small aneurysm at the right M2-3 bifurcation and pathological
findings showed an agglomeration of Gram-positive rods with a thread-like form in
the disrupted aneurysm wall. Blood culture was performed after the surgery, and Gram-positive
rods were also noted in the blood culture, so we determined that the cause of her
cerebral aneurysm ruptured was IE due to the mold.
Actinomycetes, which are virulent, are categorized into two main types. One is anaerobes
(Actinomycete genus) and another is aerobes (Nocardia genus); both cause opportunistic
infections and result in systemic dissemination. Distinguishing the species is important
to select the proper antibiotic therapy against actinomycetes,[[10]] but the diagnosis of nocardiosis is difficult because the growth speed of Nocardia
is slower than other bacteria. Culturing for >1 week will be needed to identify Nocardia.
Nocardia could be identified by Kinyoun staining, which distinguishes actinomycetes
because the cell wall is stained by the mycolic acid stain.[[11]]
In our case, Nocardia was identified by Kinyoun staining, which took 11 days after
the blood culture.
Previous reports showed that 4 of 10 patients (40%) treated only with antibiotics
died, whereas 2 of 16 surgically treated patients (12.5%) died;[[12]] the mortality rate of the unruptured aneurysm is 30% and that of ruptured aneurysms
is 80%.[[7]] Therefore, surgical intervention in the acute phase could reduce the mortality
rate of ruptured mycotic aneurysms. As an antibiotic treatment, TMP/SMX could be administered[[13]] and TMP/SMX therapy should be continued for 12 months in an immunocompromised host
with a central neurological disease, such as the presence of multiple brain abscesses.[[13]]
In our case, emergent trapping of ruptured aneurysm of M2-3 middle cerebral artery,
hematoma removal, and decompression craniotomy was performed. After that, combination
therapy with IPM/CS and amikacin was started considering the resistance of Nocardia
to antibacterial drugs.[[14]],[[15]] Then, TMP/SMX therapy was started as a hyposensitization therapy 40 days after
onset and continued for 6 months. Finally, nocardiosis was ameliorated.
In conclusion, we reported a case of a ruptured mycotic cerebral aneurysm owing to
nocardiosis. A mycotic ruptured cerebral aneurysm is an important cause of SAH in
patients who are immunocompromised. Early diagnosis of IE, detection of Gram-positive
rods by Gram staining, and long-term culture to identify the bacteria are crucial
in diagnosing nocardiosis.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the legal guardian has given his consent for images and other clinical
information to be reported in the journal. The guardian understands that names and
initials will not be published and due efforts will be made to conceal identity, but
anonymity cannot be guaranteed.
