Having HIV is considered a Red Flag feature of headaches – mandating CT. The main bad things that you’re looking for are Toxoplasmosis, Cryptococcus and CNS lymhoma. This recent article [Pubmed link] by Luma et. al. highlights the importance of making the diagnosis of toxoplasmosis in AIDS patients. However, since the widespread adoption of HAART regimens there has been astounding reduction in HIV and AIDS related morbidity and mortality – meaning that opportunistic infections are also on the decline.
So … if the patient is well appearing, tells you she is immunocompetent and has a headache syndrome that sounds like a primary benign headache … Do they really need that CT? Here’s what my quick literature search discovered:
DISCLAIMER: READ THE LITERATURE YOURSELF TO SEE IF YOU REACH THE SAME CONCLUSIONS
Maybe one of the reasons for a”CT for ALL” approach was this [pre-HAART] article by Elizabeth Tso et al [Pubmed Link] in 1993. They looked at the usefulness of CT in examining HIV patients with neurologic complaints
In a predominantly African-American and inmate population, they performed a retrospective review of CT imaging results in:
- HIV +ve patients
- those with risk factors for HIV:
- IV drug abuse [80%]
- transfusion before 1985
CT’s were performed for:
- focal neurologic signs
- other neurologic signs [e.g. visual changes]
146 pts who got 169 CT’s:
- 85 Normal [50%]
- 49 atrophy [29%]
- 35 Focal lesion [21%] – 10 of which were mass lesions
Among subgroup of 114 seropositive HIV patients there were 134 CT scans:
- 68 [50%] normal
- 43 [32%] atrophy
- 25 [17%] focal lesion
In the subgroup of 32 pt’s with risk factors 35 CT’s:
- 17 [49%] normal
- 8 [23%] atrophy
- 10 [28%] focal lesions
Looking specifically at the 99 patients presenting with headache +/- other symptoms … 85 had either normal scans or atrophy. 14 had a focal lesion:
- Headache only 32 patients: 29 normal/atrophy, 3 focal lesions [10%]
- Headache and photophobia 8 patients: 6 normal/atrophy, 2 focal lesions [25%]
- Headache and Fever 36 patients: 33 normal/atrophy, 3 focal [10%]
- Headache fever and stiff neck 6 patients: 5 normal, 1 focal lesion [17%]
Looking at 18 patients who got repeat scans:
7/18 repeat scans were +ve
- 4 = Normal/Atrophy
- 3 = New enhancing lesions [pts had: Seizure, worsening paralysis, altered LOC]
The quickest change occurred in a repeat scan done 24 days after the first CT.
Among the 76 visits that ended up getting admitted [45% of total]:
- 68%  CT scans were normal/atrophy
- 32%  focal lesions – 21 of these were admitted because of the scan [which is 12.4% of the total group]
Authors also conducted linear regression analysis. The following features were associated with CT abnormality:
Focal neurologic signs
Altered mental state
Authors recommend a “CT for ALL” approach because even non-focal presentations [i.e. headache alone] are associated with focal lesions. Furthermore, even if the patient is re-presenting to the ER after having a recent CT they should be re-scanned as changes can happen rapidly.
- This was a retrospective review of imaging in a demographic with perhaps a high disease burden – so there may be selection bias.
- This paper also pre-dated HAART – so nowadays there may be even less positive scans in these patients.
- Even though this cohort was ‘pre-HAART era’, the vast majority of patients with headache had no focal lesions on CT [85%]. Only 12% of the time the CT lead to an admission. So could CT’s be performed on a case-by-case basis and perhaps non-emergently in the “headache-only” crowd?
A late 1990′s publication by Rothman et al [Pubmed link] attempted to determine which signs and symptoms are predictive of new lesions on CT:
- They prospectively analysed a convenience sample of 110 HIV-infected patients presenting to an inner-city hospital
- Enrolled were any HIV patients presenting with new neurologic findings.
- These patients were assessed using a standardized assessment tool and were subsequently sent to the CT scanner if they reported new symptoms.
Clinical features most strongly associated with new focal lesions on CT were:
Depressed or altered orientation
Change in headache
Prolonged headache ≥3days
Focal neurologic deficits
Use of criteria 1-4 would pick up 19/19 patients with new lesions. On further analysis they added 5. Focal Neurologic deficits because of its association with the other 4 findings.
I like it when authors publish this kind of data because it allows me to tease out interesting and important findings like – asymmetric deep tendon reflexes which have a 97% specificity for a lesion on CT. Take a moment to read these findings.
75 patients had CD4 counts ≤200
- 13/75 [17%] had new lesions on CT
- In these patients New seizures, change in orientation and change in headache were predictors of CT lesions
29 patients had CD4 counts >200
- only 4/29 [13%] had new focal lesions on CT
- in theses patients new seizures and prolonged headache with nausea were predictive
This data may guide physicians to order stat imaging in HIV-infected patients who need it and obviate CT in those that will not have new lesions on CT requiring emergent management. They recommend further study of this concept.
Small study and convenience sample introduces selection bias.
New headache was 80% specific, but [perhaps because of my bias] the article suggests that “headache only” is too conservative a strategy to mandate CT scan.
The majority of [15/19 = 79%] patients with lesions on CT also had CD4 ≤200 – which seems to fit with the articles below.
These authors published in Headache 2001 [Pubmed Link] tried to come up with a clinical decision rule to help obviate the need for CT. Their hypothesis was that HIV-infected patients are at low risk of intracranial lesions if:
(1) there are no focal neurological signs or mental status alterations on physical examination
(2) there is no history of seizure
(3) CD4+ cell count ≥200 cells/mircoL.
- Retrospective review of 365 patients in San Francisco at 2 urban EDs
- Abstracted medical records from 364 HIV-infected patients who got a CT head for evaluation of headache.
- Patients were categorized as low, intermediate, or high risk based on clinical criteria (focal neurological signs, altered mental status, history of seizure) and immune status (CD4 lymphocytes ≤200 microL).
- This cohort was compared to a unselected cohort of HIV-infected outpatients with headache who were all treated and followed in primary care (N=101) for 3 months.
Inclusion: who had HIV/AIDS who got a CT head
Exclusion: Meningitis in the last 30d, previous known Toxoplasmosis, brain lymphoma or other CNS disease
- Mostly men [>90%]
- Mostly >30 yo [>80%]
- Mostly MSM, IVDU or both
- CD4+ < 200 cells/mm3 in 70% and >200 cells/mm3 in 30%
- 125 patients had no CD4+ on file – assumed to be >200 if their lymphocyte count was >2.0
- CT vs “headache” group
- CT More likely to have had an AIDS opportunistic infection
- CT More likely to have a CD4+ < 50 cells/mm3
- 8 pts lost to follow up in headache group
- Overall – 50% of headache group had benign headache. Only 3/93 had lesions diagnosed on follow up.
- CT findings:
- 40/364 [11%] had +ve CT – of these 19 had definite intracranial mass lesions [5%] the rest were possible lesions.
- Subjects classified as “low risk” [i.e rule negative] – ZERO had lesions on CT
- Subjects classified as “medium risk” [ i.e rule negative but CD4+ <200 or Lymphocytes <2.0 - 9% had CT lesions
- Subjects classified as "high risk" [focal neuro e.g.] – 21% had lesions on CT
- Features Associated with positive CT:
- Abnormal motor or sensory exam
- Abnormal mental status
- Previous Hx of opportunistic infection
- CD4+ < 200
- Toxoplasmosis +ve IgG
- [non-significant trend with Hx of Seizures]
- although type of headache wasn’t discriminating – a 1999 study [Pubmed Link] showed that change in HA may predispose to positive CT
- Despite limitations [Sample size, Loss to follow up in headache group, Retrospective study]
- Authors conclude that you can use these features to avoid unnecessary imaging in HIV-infected patients with headache
This was a retrospective review of imaging. Their algorithm can only be thought of as a derivation of a CDR that needs further validation.
That said I think that the evidence is growing that nowadays (in the HAART era), there may be a need for more than just a headache to be at risk of clinically significant lesion on CT.
If there’s CD4 > 200 with no focal findings, seizure or altered mental state – we should consider NO EMERGENT CT [unless things change]. If there’s no clinical risk factors, but a CD4 ≤ 200 – this may be a patient worth scanning [or at least looking for more subtle clinical findings]
In the study above, Graham et al [Pubmed link] tried to illicit the clinical variables predictive of those who would benefit from CT. The postulated that because CD4 count correlates with opportunistic infection, it may be able to sort out who needs CT.
Authors reviewed CT scan results and CD4 counts in HIV patients presenting with headache
Excluding those with
altered mental status, meningeal signs, neurologic findings, or symptoms of subarachnoid hemorrhage.
CT scans were considered positive or negative and were grouped according to CD4 counts:
- less than 200 cells/microL,
- 200 -499 cells/microL,
- greater than [or equal] 500 cells/microL.
178 patients total
128 negative scans [63%]
76 positive scans [37%]
- 55 had atrophy alone [77% of positive scans] – all but 3 patients had CD4 > 200
- 18 had mass lesion [23%]
- 13/18 were Toxoplasmosis – all had CD4 < 200
CD4 count > 200 obviates CT.
small series, but the figure above speaks for itself. All the pathology was in patients with low CD4 counts.
When it comes to neuroimaging in the HIV-infected population, the medical dogma suggesting a “CT for ALL” approach is being challenged. The most recent ACEP Guidelines aren’t particularly helpful [link] suggesting “neuroimaging for a new type of headache”. But the articles above [despite there being no validated CDRs] suggest that, in the post HAART era, HIV- infected patients may need more than just a headache in order to mandate a stat CT. A reasonable approach might be to stat scan those patients with:
- Altered mentation
- Focal findings
- CD4 < 200
- prolonged headache
- “Headache Plus” [photophobia, change in affect etc]
Without these, an EMERGENT CT is probably not warranted, should be considered on a case-by-case basis. I have assumed that finding “atrophy” on a CT isn’t clinically significant to the ER doc. TSO states in her article that these are young people who shouldn’t have atrophy – so the finding of atrophy may be important in their overall management … so if they haven’t had a CT they might need one – it just maybe not be done in the ER [in the middle of the night].Those are my thoughts – what do you think? Peer review via comments please [click on the link below the title of this blog post]
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