The Rule of 7's for Lyme Meningitis is a clinical calculator used in the diagnosis and management of Lyme disease, specifically in patients suspected of having Lyme meningitis. This scoring system applies to patients presenting with symptoms suggestive of meningitis, particularly in areas where Lyme disease is endemic.

The Rule of 7's helps clinicians differentiate Lyme meningitis from other causes of aseptic meningitis. It is based on the observation that in Lyme meningitis, the cerebrospinal fluid (CSF) lymphocytic pleocytosis is typically less than 300 cells/mm3, the CSF protein is less than 100 mg/dL, and the duration of symptoms before presentation is usually more than a week.

The clinical utility of this calculator is to aid in the diagnosis of Lyme meningitis, thereby guiding appropriate treatment and potentially avoiding unnecessary investigations or treatments for other causes of meningitis. 

Exclusion criteria for the use of this calculator would include patients with symptoms not suggestive of meningitis, patients with a clear alternative diagnosis, or patients in areas where Lyme disease is not prevalent.

Rule of 7's for Lyme meningitis

# Criteria
 ## Number of days of headache
A. < 7 (+0)
B. >= 7 (+1)
## CSF mononuclear cells
C. < 70% (+0)
D. >= 70% (+1)
## 7th or another cranial nerve palsy
E. Yes (+1)
F. No (+0)

# Conditions
- score == 0
- score >= 1