Effectiveness of Lumbar Puncture in the Diagnosis of Central Nervous System Infection for the Elderly Patients Presenting with Acute Confusional State

Objective: To evaluate the effectiveness of lumbar puncture (LP) as a diagnostic procedure for central nervous system infection in cases of acute confusional states in elderly patients. Patients and Methods: This is an observational prospective study as a short research article that enrolled 50 elderly patients with acute confusional state to assess lumbar puncture results as a diagnostic procedure for central nervous system infections in Al-Fallujah Hospital in Al-Anbar, Iraq, between January 2011 and January 2013. All of the patients have been subjected to lumbar puncture (LP), as well as laboratory investigations. Results: This study reveals slight female predominance (54%) in cases of acute confusional state. The mean age was 68 years. Acute confusional state in 92% of our cases was due to systemic disease, and central nervous system infection (meningitis and encephalitis) represented only 8% of cases. Most LPs were negative (normal). Fifty per cent of CNS infections were in pre-LP cases presenting systemic diseases. Central nervous system infections were mostly bacterial meningitis. Conclusions: This study reveals that positive LP results were low in elderly patients presenting with acute confusional state. This gives an idea about the LP effectiveness that should be suspected. Since the causes of such presentation are life threatening diseases, so LP remain the best useful procedure in spite of its low positive results.


INTRODUCTION
ACS in the elderly is a diagnostic dilemma that physicians and neurologists in emergency units face daily. One of the most challenging questions is whether to proceed with LP. Yet there are many difficulties for LP indication in elderly patients. While ACS occurs in 33% to 41% of elderly patients [1], the overall incidence of meningitis is about 2 to 10 cases per 100,000 people per year [2]. Approximately 20% of the cases were projected to involve individuals >60 years [3]. However, in the sense of atypical presentation of CNS infection in the elderly, and because of its high mortality rate, meningitis should effectively be excluded. Some authors believe that older people more often present with the triad of fever, neck stiffness, and altered mental status than younger adults [4], while others believe in the triad of fever, nuchal rigidity, and altered mental status, though this triad is only seen in 40% of elderly patients with meningitis [5]. The geriatric patient may also have false-positive findings of meningitis. Signs and symptoms of meningeal irritation, such as nuchal rigidity or a positive Kernig's sign or Brudzinski's sign, may be found in healthy elderly people.
This false-positive finding is attributed to the presence of limited neck mobility and cervical spine disease. Thus, classic signs and symptoms of meningeal irritation are unreliable in the elderly and make the diagnosis of meningitis more difficult [2]. LP efficiency decreased dramatically according to patients' age [6]. LP is never mentioned as a primary investigation and was always left to the condition. While being the most valuable diagnostic tool for CNS infection, LP has a limited role in ACS due to its very low yield as some authors' believes [7].
Some have suggested that cerebrospinal fluid should be analysed only in atypical cases of stroke, or when pyrexia develops without an apparent source of infection in an elderly patient with stroke [8]. Others believe that it should be done for every patient with ACS [9], while yet others do not believe in doing LP unless for typical cases of meningitis [10]. The causes of ACS in the elderly are mainly due to systemic infection (34%), stroke (11%), and electrolyte disturbance (10%) [11]. CNS infection represents 1% to 5% of cases of ACS. These numbers give an idea of the difficult decision regarding LP.

PATIENTS AND METHODS
This is a prospective observational study as a short research article on 50 elderly patients. The patients were aged 60 to 85 years old. The mean age was 68, with a small female predominance. Patients present with ACS at time of hospital admission at Al-Fallujah hospital in Al-Anbar, Iraq, between January 2011 and January 2013. All patients were examined by a neurologist via LP.
General medical and neurological examination was done for the patients. We applied the Confessional Assessment Method (CAM). It includes the following criteria:

RESULTS
The range for the age of the patients was between 60 and 85 years old. The mean age was 68 years old, with a little female predominance, as 54% of our patients were female.   Table  4.
CNS infections (meningitis and encephalitis) are mostly bacterial in the elderly, and both cases in our sample were due to S. pneumonia. We had one case of viral encephalitis and one case of TB meningitis. These results were proved by CSF culture and DNA testing with PCR, as with clinical responses to treatment Table 5.

DISCUSSION
The mean age was 68 years in this study and it was less than that of James George study, who point to being 81 years [12]. Half of our sample was between 60 and 69 years old, and the other older age group represented the smaller sample due to their decreasing number by death by aging. The difference in mean age between our sample and that of George was mostly due to hard living conditions in our country. While slight female predominance in our study (54%) is comparable to that of James George results who points to 78 men and 93 women in his study.  The most difficult cases come from the presence of neck flexion resistance. This is hardly evaluated in elderly especially in those with generalized spasticity. Most commonly this occurs in dehydrated patients and in those with previous history of multiple stroke or Parkinsonism or even merely cervical spondylosis. It is especially common among the older age group of our sample. In addition to the well-known causes of difficulty in diagnosis in the elderly, our sample included cases of delayed presentation to the hospital, as one of the important causes of vague presentation. Because patients stayed at home, especially in rural areas, waiting for spontaneous improvement, with poor oral intake and without intravenous fluid, and began to deteriorate with dehydration and disturbed consciousness before being brought to the hospital, where we received them with complicating presentations, such as disturbed consciousness, generalized spasticity, and fever. At this point, physicians and neurologists face the problem of waiting for general supportive measures or proceeding with immediate LP. This causes diagnostic difficulty and makes the decision difficult for both medical staff and patients' relatives, with respect to complications versus benefits.
The presence of an apparent disease did not eliminate the need for LP. In our sample, we diagnosed 50% of our CNS infection cases in patients who already presented with apparent specific diseases at initial evaluation. This is very risky result because it may mandate LP for every patient with ACS. This is comparable to D'Amore, who points to 46% of his cases of [13].
The presence of fever does not make a great different in the diagnosis of CNS infection, as appears in our study. This is comparable to Shah, who states that meningitis was present in both with or without fever [14]. He gave higher rates to those without fever, as he pointed out that meningitis occurred in 12%, compared to 7% in those with fever. CNS infection in the elderly is commonly caused by bacterial infection. This is comparable to Delerme [15], and this means that there is more mortality, so there is more urgency to do LP. This was differing from Majed [6] who points to (lymphocytic) meningitis (8.5%), while bacterial meningitis cases were only (2.4%).
Cases of ACS which remain of unknown aetiology represent 14% of the sample and this is comparable to Dheeraj Rai [16]  Although our sample is not large, but it still can give an idea about the low positive results that the physicians should suspect when performing LP.
Since the causes of such presentation are life threatening diseases, so LP remain the best useful procedure in spite of its low positive results, and especially because the negative results is important in excluding serious diseases and this is significant as the positive results.

CONCLUSION
This study reveals that positive LP results were low. While some authors see that LP must be done for all patients so as to not miss even a single case, others see that it is unnecessary to subject all patients to LP just to detect a few cases, and argue that doctors should save LP for clear cases. In the absence of consistent results, the decision to perform LP looks more philosophical and subjective than being based on a solid clinical base. But since the causes of such presentation are life threatening diseases, so LP remain the best useful procedure in spite of its low positive results.

RECOMMENDATIONS
More studies with larger sample are needed to reach a solid base for LP indications in the elderly that make the selection of the patients more accurate to avoid unnecessary LP.
Geriatrics need attention and people need education about their elderly patients to ensure that elderly patients in need of medical attention are brought to the hospital as early as possible.

CONSENT
All authors declare that 'written informed consent was obtained from the patient (or other approved parties) for publication of this case report and accompanying images.

ETHICAL APPROVAL
All authors hereby declare that all experiments have been examined and approved by the appropriate ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki.